Leonardo da Vinci? What did he do for science?

For science cl, I have to write a 800-1000 word paper on Leonardo and his wonderful/dramatic life. One of the things I have to put into this paper, is his biggest greatest contribution to science. I looked at some sites and learned that he study anatomy, but then I looked at other sites, and learned he did so much more than anatomy. The reason why I'm asking is because I'm not a Doctor and I don't know what those twenty letter words mean. I really need help on this, so I ask that you please help me. Also, please no mean comments, I'm sorry I can be as smart as you want me to be.