He was also interested in botany, human anatomy, and used animal parts from a butcher shop to study. He also tried to dissect a human corpse, but got in trouble with the Catholic Church because it was considered a sin. But he was able to develop a model of how the human heart works. 

In 1514s to 1516 Leonardo lived in Rome, and built both toys and machines. He studied optics and tried to make large round mirrors, like the ones used in telescopes.  Craftsmen in Leonardo's time knew how to use and repair familiar machines. Leonardo figured if he could understand how each machine part worked; he could use these parts to make new machines.

Leonardo made sketches and plans of things like a tank, helicopters, a plane, and an arithmetic machine.  These are common machines in our lives.  His early thinking about the arithmetic machine was the start of things that came after it like the abacus, the slide rule, the adding machine, the calculator and finally the computer.

Leonardo da Vinci wrote in a way that no one else did. He used a technique called mirror writing in which his letters appear backwards. No one knows the true reason why he used mirror writing but he might have tried to make it harder for people to read his notes and get his ideas. He might have been hiding his scientific ideas from the Roman Catholic Church who disagreed with what Leonardo was trying to learn. In that time people were not suppose to question anything thought to be created by God.   Writing left handed from left to right was messy because the ink that he just put down would smear as his hand moved across it and writing in the other direction would prevent smudging
On May 2, 1519 in Cloux France, Leonardo da Vinci died. He died of old age. If Leonardo da Vinci were alive today he might try to make artificial organs or a cure for AIDS and cancer. He might try to figure out a way to fly without planes and helicopters or a way to prevent air pollution.
Leonardo da Vinci   left many unseen notebooks after he died. All of the notebooks that Leonardo left contained mirror writing. One of the notebooks is in the British Museum and known as the Codex Arundel. These are loose papers, which come from various times of his life, are about the physical and geographical effects of water. Leonardo hoped to write a book about this subject. The Renaissance was a special time in the history of man. The word renaissance means rebirth. The Renaissance came following the Dark Ages. It was an explosion of creativity in art, literature, science and music.  Leonardo da Vinci was born in these times. He was known as the "Renaissance Man", because he himself was an 'explosion' of all these things, and brought so much to them.   Before the Renaissance, people had to spend their entire lives just struggling to exist.