Leonardo da Vinci is best known for painting the "Mona Lisa" and "The Last Supper". But he was more than a gifted artist, he was also an engineer and a scientist. Much of his scientific studies were dedicated to understanding the movement and characteristics of water which culminated in his published work, Water Theory: On the origin and fate of water. Ahead of his time, in his water theory da Vinci came close to defining the hydrological cycle, pointing out that water passes through major river systems multiple times, equaling sums much greater than the volumes contained in the world's oceans.
In true artistic fashion, da Vinci was able to sum up the importance of water with his famous quote, "Water is the driving force of all nature."