If you could give yourself bigger muscles with a simple injection, altering the very genes in your body– would you?

That’s one of the things that scientist Josiah Zayner has already tried to do. The San Francisco-based genetic engineer says he uses Crispr to try and modify the cells in his body, and he wants to help people all over the world do the same.

Zayner’s encountered some controversy, but argues that he’s just helping people take more control over their bodies… or rather, the bodies they want.