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So Very Small: How Humans Discovered the Microcosmos, Defeated Germs—and May Still Lose the War Against Infectious Disease
“An elegant, wide-ranging history” (The New York Review of Books) of the centuries-long quest to discover the critical role of germs in disease thatreveals as much about human reasoning—and the pitfalls of ego—as it does about microbes.
“Levenson takes readers through an entertaining . . . journey of missed opportunities in microbiology and the eventual advances that arose in this field.”—Science
Scientists and enthusiastic amateurs first confirmed the existence of living things invisible to the human eye in the late seventeenth century. So why did it take two centuries to connect microbes to disease? As late as the Civil War in the 1860s, most soldiers who perished died not on the battlefield but of infected wounds, typhoid, and other diseases. Twenty years later, the outcome might have been different, following one of the most radical intellectual transformations in germ theory, the recognition that the tiniest forms of life have been humankind’s greatest killers. It was a discovery centuries in the making, and it transformed modern life and public health.
As Thomas Levenson reveals in this globe-spanning history, it has everything to do with how we see ourselves. For centuries, people in the West, believing themselves to hold God-given dominion over nature, thought too much of humanity and too little of microbes to believe they could take us down. When nineteenth-century scientists finally made the connection, life-saving methods to control infections and contain outbreaks soon followed. The next big break came with the birth of the antibiotic era in the 1930s. And yet, less than a century later, the promise of the antibiotic revolution is already receding due to years of overuse. Is our self-confidence getting the better of us again?
So Very Small follows the thread of human ingenuity and hubris across centuries—along the way peering into microscopes, spelunking down sewers, visiting army hospitals, traipsing across sheep fields, and more—to show how we came to understand the microbial environment and how little we understand ourselves. Levenson traces how and why ideas are pursued, accepted, or ignored—and hence how human habits of mind can, so often, make it terribly hard to ask the right questions.
“Levenson takes readers through an entertaining . . . journey of missed opportunities in microbiology and the eventual advances that arose in this field.”—Science
Scientists and enthusiastic amateurs first confirmed the existence of living things invisible to the human eye in the late seventeenth century. So why did it take two centuries to connect microbes to disease? As late as the Civil War in the 1860s, most soldiers who perished died not on the battlefield but of infected wounds, typhoid, and other diseases. Twenty years later, the outcome might have been different, following one of the most radical intellectual transformations in germ theory, the recognition that the tiniest forms of life have been humankind’s greatest killers. It was a discovery centuries in the making, and it transformed modern life and public health.
As Thomas Levenson reveals in this globe-spanning history, it has everything to do with how we see ourselves. For centuries, people in the West, believing themselves to hold God-given dominion over nature, thought too much of humanity and too little of microbes to believe they could take us down. When nineteenth-century scientists finally made the connection, life-saving methods to control infections and contain outbreaks soon followed. The next big break came with the birth of the antibiotic era in the 1930s. And yet, less than a century later, the promise of the antibiotic revolution is already receding due to years of overuse. Is our self-confidence getting the better of us again?
So Very Small follows the thread of human ingenuity and hubris across centuries—along the way peering into microscopes, spelunking down sewers, visiting army hospitals, traipsing across sheep fields, and more—to show how we came to understand the microbial environment and how little we understand ourselves. Levenson traces how and why ideas are pursued, accepted, or ignored—and hence how human habits of mind can, so often, make it terribly hard to ask the right questions.
448 pages, Hardcover
First published April 29, 2025
74 people are currently reading
3241 people want to read
About the author
Thomas Levenson
16 books61 followersMy day job has me professing science writing at MIT, where I teach in the Institute's Graduate Program in Science Writing.
I continue to do what I did before I joined the professoriat: write books (and the occasional article), and make documentary films about science, its history, and its interaction with the broader culture in which scientific lives and discoveries unfold.
Besides writing, film making and generally being dour about the daily news, I lead an almost entirely conventional life in one of Boston's inner suburbs with a family that gives me great joy.
I continue to do what I did before I joined the professoriat: write books (and the occasional article), and make documentary films about science, its history, and its interaction with the broader culture in which scientific lives and discoveries unfold.
Besides writing, film making and generally being dour about the daily news, I lead an almost entirely conventional life in one of Boston's inner suburbs with a family that gives me great joy.
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Displaying 1 - 27 of 27 reviews
May 16, 2025
This standout book of 2025 is a triumph of science writing, blending rigorous research with an approachable style that welcomes readers regardless of their biochemistry knowledge. It’s a compelling exploration of scientific discovery, human flaws, and our place in a microbial world.
Key Themes
Nonlinear Scientific Progress: The narrative traces the erratic arc of breakthroughs. It took centuries to link microbes to disease after the microscope’s invention, yet the COVID-19 vaccine emerged in months, showcasing science’s unpredictable leaps.
Human Bias as a Barrier: Dogma—whether religious, political, or scientific—often stifles progress. Paraphrasing Max Planck, the book notes that science advances “one funeral at a time,” as new ideas battle entrenched beliefs.
Collective Responsibility vs. Hubris: The text critiques those who reject vaccines or quarantines for personal freedom, endangering society. It reinforces a vital truth: what benefits the group ultimately benefits the individual.
Favorite Quote
“We coexist with billions of our own kind and a vastly greater number of other living forms with evolutionary interests of their own.” This line encapsulates the humbling reality of our shared existence with microbes.
Key Themes
Nonlinear Scientific Progress: The narrative traces the erratic arc of breakthroughs. It took centuries to link microbes to disease after the microscope’s invention, yet the COVID-19 vaccine emerged in months, showcasing science’s unpredictable leaps.
Human Bias as a Barrier: Dogma—whether religious, political, or scientific—often stifles progress. Paraphrasing Max Planck, the book notes that science advances “one funeral at a time,” as new ideas battle entrenched beliefs.
Collective Responsibility vs. Hubris: The text critiques those who reject vaccines or quarantines for personal freedom, endangering society. It reinforces a vital truth: what benefits the group ultimately benefits the individual.
Favorite Quote
“We coexist with billions of our own kind and a vastly greater number of other living forms with evolutionary interests of their own.” This line encapsulates the humbling reality of our shared existence with microbes.
July 10, 2025
Ignorance arising from an inability to know any better is excusable. Ignorance arising from volitional refusal to know any better is not.
In the modern semi-post-Covid era (because we are NOT wholly post-Covid, just FYI), it is difficult to read a book like this and not want to rip all of your hair out seeing the hell people went through a century or more ago because they simply didn't have the technology or understanding to fend it off and knowing that people today CHOOSE that kind of suffering out of some weird stubborn aversion to science or logic. Like I would love to take anti-vaxxers and time-travel them back to the cholera epidemics in the 1800s and see what they think of modern science and vaccines and such.
I really appreciated how Levenson walks us through these historical events and shows the process of arriving at new discoveries in medicine, disease, hygiene, etc. There's a lot of detail and play-by-play, but it doesn't get dry or dull because it almost has the feel of a mystery, even if we know the discoveries or inventions that are coming. We get to see how these diseases affected everyone from the lowest to highest classes, and the follies that spurred them on, specifically the inane notion that doctors could not POSSIBLY be vectors of infection because they are GENTLEMEN who are CLEAN. I guess Trust Me Bro University has been around quite a long time! But even there, they were operating with so little in the way of scientific knowledge that I suppose it can be excused if they found the idea preposterous. (They still should have been slapped, though.)
I will say that me myself personally, I could have done with a little less of the very graphic descriptions of the symptoms and effects of the various diseases because YUCK. So just a heads-up not to read this while eating. Or soon before eating. Or soon after.
In the modern semi-post-Covid era (because we are NOT wholly post-Covid, just FYI), it is difficult to read a book like this and not want to rip all of your hair out seeing the hell people went through a century or more ago because they simply didn't have the technology or understanding to fend it off and knowing that people today CHOOSE that kind of suffering out of some weird stubborn aversion to science or logic. Like I would love to take anti-vaxxers and time-travel them back to the cholera epidemics in the 1800s and see what they think of modern science and vaccines and such.
I really appreciated how Levenson walks us through these historical events and shows the process of arriving at new discoveries in medicine, disease, hygiene, etc. There's a lot of detail and play-by-play, but it doesn't get dry or dull because it almost has the feel of a mystery, even if we know the discoveries or inventions that are coming. We get to see how these diseases affected everyone from the lowest to highest classes, and the follies that spurred them on, specifically the inane notion that doctors could not POSSIBLY be vectors of infection because they are GENTLEMEN who are CLEAN. I guess Trust Me Bro University has been around quite a long time! But even there, they were operating with so little in the way of scientific knowledge that I suppose it can be excused if they found the idea preposterous. (They still should have been slapped, though.)
I will say that me myself personally, I could have done with a little less of the very graphic descriptions of the symptoms and effects of the various diseases because YUCK. So just a heads-up not to read this while eating. Or soon before eating. Or soon after.
August 16, 2025
An excellent, non-technical history of mankind’s intellectual evolution to developing, understanding and exploiting germ theory, with a caution that we cannot grow complacent with our success over the last 50 years.
August 20, 2025
I thought this would be more about modern microbiological advances but it was all history up to about WWII. So that’s kind of on me but I still think the byline is a bit misleading. Very thorough historical account but I wish they talked more about antibiotic resistance, new alternatives to typical antibiotics, stuff like that.
September 21, 2025
Chose this at random off the shelf at the library. Great book about the history of germ theory. Nice to know that humans have always been stubborn about the effect of germs and vaccines on our bodies (“we are higher beings! God ordained it!” back then to “pharmaceutical companies are trying to turn us into human magnets!” now) and sad to know that will probably be the death of us if we keep allowing people to spread vaccine misinformation and thus help viruses and bacteria mutate faster than we can fight them off…
July 8, 2025
So very small, is a most timely book and highly recommended!
MIT Professor of Science Writing, Thomas Levenson provides a superb survey of how we have come to understand why we contract various diseases as well as how we can prevent or treat them. The contributions made in the 17th Century by von Leeuwenhoek with his microscope, the germ theory proposed by Robert Koch in the 19th Century, as well as our understanding of fermentation, pasteurization, and development of vaccines by Louis Pasteur along with the many other advances over the centuries is reviewed with a great many vivid vignettes.
However, we are at the crossroads as we now face growing antibiotic resistance, misinformation regarding vaccinations, and the reduction of spending on new medication development and basic science at the NIH and treatment programs at the CDC.
A wonderful testimony to those who have contributed to the progress in advancing our understanding of science, this book is a chilling reminder of how much is at stake as we start the 21st Century.
MIT Professor of Science Writing, Thomas Levenson provides a superb survey of how we have come to understand why we contract various diseases as well as how we can prevent or treat them. The contributions made in the 17th Century by von Leeuwenhoek with his microscope, the germ theory proposed by Robert Koch in the 19th Century, as well as our understanding of fermentation, pasteurization, and development of vaccines by Louis Pasteur along with the many other advances over the centuries is reviewed with a great many vivid vignettes.
However, we are at the crossroads as we now face growing antibiotic resistance, misinformation regarding vaccinations, and the reduction of spending on new medication development and basic science at the NIH and treatment programs at the CDC.
A wonderful testimony to those who have contributed to the progress in advancing our understanding of science, this book is a chilling reminder of how much is at stake as we start the 21st Century.
June 6, 2025
4.5-5 stars for this accessible, fascinating account of the evolution of germ theory. Five years on from the pandemic, I can’t help but wonder when and what the next one will be, and wonder - will we be able to meet the challenge? Despite all the political conflict over masks, vaccines, etc., isolating the virus, sequencing the DNA and developing the vaccine was remarkably fast, by historical standards.
Being a bit of an armchair science geek, I’ve always been fascinated by the mindset that we humans have absolute control over the universe, all that we can and cannot see. History shows us, and this author illustrates beautifully, that the microscopic world around us plays a vital role in human life (or death). From bubonic plague to cholera to Spanish Flu to Covid-19, humanity has repeatedly been decimated by tiny living things invisible to the naked eye. These microbes evolve and mutate, and we need solid research and public health practices to stay ahead and keep developing vaccines and cures.
I’ve included several quotes in my reading progress to give a taste of the author’s accessible, informative and entertaining style. A prevalent theme throughout the book is what kept this or that scientist from making that next leap in thought or imagination that could’ve advanced the research and saved lives. Sometimes it was professional or political pressure, sometimes rigid, backward thinking.
About our own recent pandemic, the author notes toward the end: The value of increasingly rapid and effective science has been a running theme of this book, but so has the metastasis of disinformation and the stubborn clinging to false ideas. From nineteenth-century miasma adherents to contemporary attacks on masking and, above all, a relentless anti-vaccination campaign, the epidemic spread of false “facts” about COVID did yet more damage. I hope we can do better next time.
Being a bit of an armchair science geek, I’ve always been fascinated by the mindset that we humans have absolute control over the universe, all that we can and cannot see. History shows us, and this author illustrates beautifully, that the microscopic world around us plays a vital role in human life (or death). From bubonic plague to cholera to Spanish Flu to Covid-19, humanity has repeatedly been decimated by tiny living things invisible to the naked eye. These microbes evolve and mutate, and we need solid research and public health practices to stay ahead and keep developing vaccines and cures.
I’ve included several quotes in my reading progress to give a taste of the author’s accessible, informative and entertaining style. A prevalent theme throughout the book is what kept this or that scientist from making that next leap in thought or imagination that could’ve advanced the research and saved lives. Sometimes it was professional or political pressure, sometimes rigid, backward thinking.
About our own recent pandemic, the author notes toward the end: The value of increasingly rapid and effective science has been a running theme of this book, but so has the metastasis of disinformation and the stubborn clinging to false ideas. From nineteenth-century miasma adherents to contemporary attacks on masking and, above all, a relentless anti-vaccination campaign, the epidemic spread of false “facts” about COVID did yet more damage. I hope we can do better next time.
July 3, 2025
So Very Small by Thomas Levenson is a fascinating and well-written exploration of the microscopic world and its enormous impact on human health. Though the book primarily focuses on diseases, it reads like a detective story—tracing the historical mystery of which microbes cause which illnesses. Levine does an excellent job illustrating how difficult it was for the scientific community to accept new ideas, showing that it took nearly 200 years to go from simply seeing microbes to proving they were the actual cause of disease.
One of the book’s strengths is how it weaves scientific discovery with narrative intrigue, making complex history both accessible and engaging. Levine also highlights how resistance to new thinking has long been a barrier in medicine, which adds a thought-provoking dimension.
However, the book takes a slightly political turn toward the end. While Levine rightly critiques the stubbornness of the historical medical establishment, he also turns his criticism toward modern-day skeptics. This shift feels somewhat contradictory and, in my view, detracts from the central message. While I agree that people should follow science, it’s equally important to critically evaluate which science, studies, and surveys we choose to trust.
Despite this minor criticism, I thoroughly enjoyed So Very Small. It’s an insightful, thought-provoking read that blends science, history, and mystery in a way that’s both educational and entertaining.
One of the book’s strengths is how it weaves scientific discovery with narrative intrigue, making complex history both accessible and engaging. Levine also highlights how resistance to new thinking has long been a barrier in medicine, which adds a thought-provoking dimension.
However, the book takes a slightly political turn toward the end. While Levine rightly critiques the stubbornness of the historical medical establishment, he also turns his criticism toward modern-day skeptics. This shift feels somewhat contradictory and, in my view, detracts from the central message. While I agree that people should follow science, it’s equally important to critically evaluate which science, studies, and surveys we choose to trust.
Despite this minor criticism, I thoroughly enjoyed So Very Small. It’s an insightful, thought-provoking read that blends science, history, and mystery in a way that’s both educational and entertaining.
May 1, 2025
An interesting work of popular science/history of medicine that follows the centuries-long saga of germ theory - from the discovery of germs themselves, to their first identification as the source of disease, to the era of antibiotics and current problems with them. It is a neat and comprehensive story, told through the lives and work of many scientists, both famous and lesser known, and their patients.
But I have to admit that I was a bit surprised and disappointed that the author completely ignores the topic of bacteriophages, which are 1) fascinating 2) the most promising alternative to antibiotics. So I recommend to combine this book with another one, The Living Medicine: How a Lifesaving Cure Was Nearly Lost―and Why It Will Rescue Us When Antibiotics Fail by Lina Zeldovich , which focuses on bacteriophages.
Thanks to the publisher, Random House, and NetGalley for an advanced copy of this book.
But I have to admit that I was a bit surprised and disappointed that the author completely ignores the topic of bacteriophages, which are 1) fascinating 2) the most promising alternative to antibiotics. So I recommend to combine this book with another one, The Living Medicine: How a Lifesaving Cure Was Nearly Lost―and Why It Will Rescue Us When Antibiotics Fail by Lina Zeldovich , which focuses on bacteriophages.
Thanks to the publisher, Random House, and NetGalley for an advanced copy of this book.
August 27, 2025
A short review is in a sense a massive compliment - one which I intend to pay to this book. This was an interesting overview of the development of germ theory from its beginnings in spontaneous generation and miasmatic thinking to the present. It walks the line of presenting factual history and making pithy asides and humorous interjections on the more conservative side, having faith that the story its telling is interesting enough without making repeated pop culture references, while allowing the ridiculousness of some moments speak for themselves and underlining others to let a lay person like myself in on the joke. It is informative and interesting throughout and on a personal note, had a lovely bit of synergy with an ARC I'm about 3/4 done with.
It's not incredible - I won't be gushing about it to my friends that they simply MUST read it. But it delivers on its promise, its well-written, and I was very genuinely engaged and intrigued throughout. You can't ask for much more than that.
It's not incredible - I won't be gushing about it to my friends that they simply MUST read it. But it delivers on its promise, its well-written, and I was very genuinely engaged and intrigued throughout. You can't ask for much more than that.
April 18, 2025
This book explores the centuries-long journey to understand the role of germs in disease, revealing how human biases and overconfidence hindered scientific progress. From the discovery of microbes to the antibiotic era and beyond, it examines the interplay between hubris, human ingenuity, and our understanding of the microbial world.
This book is informative, entertaining, and sometimes heart-wrenching. The progress of medicine during the nineteenth century was painfully slow, as this book demonstrates, and far too many lives were lost that could have been saved if people had trusted evidence rather than tradition. The book also stresses the importance of humility as we’re faced with the evolution of drug-resistant strains of infectious diseases, now and in the future.
Thanks, NetGalley, for the ARC I received. This is my honest and voluntary review.
This book is informative, entertaining, and sometimes heart-wrenching. The progress of medicine during the nineteenth century was painfully slow, as this book demonstrates, and far too many lives were lost that could have been saved if people had trusted evidence rather than tradition. The book also stresses the importance of humility as we’re faced with the evolution of drug-resistant strains of infectious diseases, now and in the future.
Thanks, NetGalley, for the ARC I received. This is my honest and voluntary review.
January 10, 2026
Essentially a history of events leading to the discovery of bacterium and viruses we have battled over the millenniums. Though we eventually gained the upper hand the cost in lives it can be assumed was in the billions. The book drills down into the accounts, circumstances and players in the epic strife.
I was hoping for a bit more on what the future holds and the author does address this briefly toward the conclusion but it is sketchy and as still fully undetermined. It is chilling to see how a few of these deadly illnesses have made gradual comebacks when we thought they were fully eradicated. Also he mentions how our human hubris makes the assumption we will always come out on top with our marvelous and ingenious technology. Maybe not so, time will tell.
I was hoping for a bit more on what the future holds and the author does address this briefly toward the conclusion but it is sketchy and as still fully undetermined. It is chilling to see how a few of these deadly illnesses have made gradual comebacks when we thought they were fully eradicated. Also he mentions how our human hubris makes the assumption we will always come out on top with our marvelous and ingenious technology. Maybe not so, time will tell.
September 27, 2025
This was the best book I’ve read so far this year. Levenson’s writing is perfect for those who are not experts in microbiology, but are interested in its history.
Really, anyone who is interested in the history of biology would probably love this book.
At times, it was incredibly sad, as with the ignorance of how puerperal fever was spread and its effects on women. Same with cholera. It made me feel fortunate to be alive in 2025 instead of 1825.
Then at the end, the events that lead up to May 8th, 1980 are described. A time of living memory for me. It truly made me feel a sense of awe of what humanity is capable of.
Really, anyone who is interested in the history of biology would probably love this book.
At times, it was incredibly sad, as with the ignorance of how puerperal fever was spread and its effects on women. Same with cholera. It made me feel fortunate to be alive in 2025 instead of 1825.
Then at the end, the events that lead up to May 8th, 1980 are described. A time of living memory for me. It truly made me feel a sense of awe of what humanity is capable of.
February 11, 2025
I loved this book. It has great story-telling that kept me engaged from start to finish. I found the story very compelling and that it read like a great novel rather than non-fiction. I found the pacing very good, especially considering the amount of detail given. There were also some great passages that warranted re-reads. At times I did find the writing overly literary for my taste but this didn’t affect how I felt about the book. Thank you to Netgalley and Random House for the advance reader copy.
July 4, 2025
Wow, I spent the first 16 years of my career as a microbiologist and epidemiologist. This is the best coverage of the history of the germ theory of infection that I have read. But the real power of the book is its message that the microcosmos is ready to defeat us again because we have lost our focus and allowed leaders to take us back 100 years in the progress we made. If you only read the last chapter you will be partially informed and should be encouraged to advocate for a continuing fight to protect us all.
July 9, 2025
From Leeuwenhoek to the Covid vaccine work, this book traces the history of germ theory while shedding light on the realities behind the celebrated moments of progress. I liked how the author points to the multiple stops and starts in the research, the prevailing opinions and the failure to image the future leading to centuries of neglect to curable problems. On the other hand, it does show that the people who continue to push the boundaries are very much needed for our progress.
August 29, 2025
So Very Small is a celebration of the centuries of accumulated knowledge that got us there—and a forceful warning not to squander it.
-Alex Russell
Read the full review at: https://www.bookbrowse.com/mag/review...
-Alex Russell
Read the full review at: https://www.bookbrowse.com/mag/review...
May 14, 2025
A very readable, interesting and worthwhile book.
June 21, 2025
Easy read on the evolving understanding of germs through the ages. Very bacteria heavy though, would have been more complete with more of the fundamental science underlying the discovery of viruses.
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August 18, 2025I personally found this to be fascinating!
October 2, 2025
This is a fairly slow retelling of how germ theory came to be, with a number of stories I've heard before but arranged in a nice way to tell the meta-story.
November 8, 2025
Interesting, easy to understand the science stuff. Good history. I really enjoyed it
December 3, 2025
The discovery process of microorganisms was discussed, but overall it was fairly standard.
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December 14, 2025DMPL EXAMINED 251214 AUDIBLE WISH LIST
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December 28, 2025Margaret recommended this.
September 30, 2025
Really enjoyed this. Made me realize how much we take for granted our world of antibiotics and vaccines. We've been living in such a small period of history where infectious disease hasn't been so horrifying. There were some slow parts in the first half but overall I thought this was really informative and entertaining.
August 26, 2025
A great read on Germ Theory and the zig-zag path it followed. More than just the science of germ theory, it highlights how change can be so hard for humans and how biological battles once considered won may have the outcome reversed. Thank you for a great book.
Displaying 1 - 27 of 27 reviews