As he grew older, he continued his scientific research not only as a means to improve his art but also driven by a lively instinct to understand the deeper beauty of nature. When he struggled to find a theory explaining why the sky appears blue, he did not do it merely to be able to paint better pictures. His curiosity was genuine, independent, and bordered on a pleasant obsession. But even when he engaged in imaginative intellectual pursuits, his science was inseparable from his art. Together they served his driving passion, which was nothing other than to learn everything about the world, including, among other things, our place in it. He respected the wholeness of nature and had the gift of identifying its harmonious patterns, which he saw reproduced in phenomena both small and large. In his notebooks, he depicted curls, water vortices, and whirlwinds and tried to formulate the mathematical relationships underlying such helical shapes.

While I was at Windsor Castle admiring the overwhelming power of a series of drawings depicting floods and deluges, which he created towards the end of his life, I asked Martin Clayton, the curator of the collection, whether he believed Leonardo had created them as artistic or scientific works. As soon as I asked the question, I realized it was foolish. "I don't think Leonardo would have made that distinction," he replied. I began writing this book because Leonardo da Vinci represents the ultimate model of the ability to combine different fields of knowledge – arts and sciences, humanities and technology – an ability that is the key to innovation, imagination, and genius and is a central theme of all the biographies I have written.