Even during Leonardo da Vinci’s lifetime, legends circulated about him. He was a mystery to his contemporaries and remains to this day one of the most enigmatic figures in human history. “How well a well-spent day brings happy sleep, and how a life so fruitfully lived brings satisfaction”—this principle the great Italian followed to the very end of his days. He believed that both science and art are ways of knowing and transforming the world, and therefore tried to understand the essence of all things and phenomena around him—whether it was the structure of the human body, a bird’s flight, the origin of the rainbow, or the theory of painting. The book publishes selected natural-science works by Leonardo da Vinci and his “Treatise on Painting.” The Russian translation was made by the leading scholars of the 20th century A.A. Guber and V.P. Zubov.