Roberto and Ivan have known each other for years. They worked together in AI research for the same company in the US for some time. Then Ivan took the road to art, while Roberto remained in technology. However, both continued to share a passion for photography. While Ivan was back in France, Roberto was living in New York City. During Ivan’s trip to New York sometime in 2011, Roberto and Ivan discussed the idea of a photographic book based on a unique concept. That is how Diptych was born. Once a month, Ivan and Roberto would agree on a theme. The theme could be abstract, like joy and darkness, or concrete, like newborn and eyes. Each month Roberto and Ivan would exchange one photo each as their interpretation of the theme. The following month, each of them would exchange an additional photo, as a response to the theme photo of the other. So, for each theme, there would be four photos, the two original theme photos, and the two responses by Ivan and Roberto. Each photo had to be high quality in order to be possibly printed as a large format, and strictly in square format. The effort took about 10 years to we produced 96 photos for 24 themes, and then had discussions about the photos as a whole, occasionally replacing some of them with others. This book is the result of all this work and we are very proud and happy to present it to you. We hope you will enjoy it.