Leonardo da Vinci was a self-taught artist, scientist, and inventor. He used drawing as a tool to help record his thoughts and develop new ideas. His notebooks often included sketches of existing machines and ideas for inventions he wanted to build. While dabbling in medicine, he drew his observations, using varying line weights as well as fine lines to indicate the ways in which the bones of the body fit together. Leonardo also used his knowledge of anatomy to sketch portraits. His drawings provide records of his advances in science, technology, and art.