Two of his pictures are among the best-known paintings in the world: the "Mona Lisa" and "The Last Supper". He did many drawings. The best-known drawing is "Vitruvian Man". Leonardo was often thinking of new inventions. He kept notebooks with notes and drawings of these ideas. Most of his inventions were never made. Some of his ideas were a helicopter, a tank, a calculator, a parachute, a robot, a telephone, evolution, and solar power.