L-DOPA is the best drug we have for Parkinson’s disease, but its molecular mirror image, D-DOPA, causes dangerous side effects. Making L-DOPA without also making D-DOPA is surprisingly hard and requires a specific kind of molecule to pull off. But that specific molecule must be made from a different and equally specific molecule. In this video, our host George explains how one of the winners of the 2001 Nobel Prize in Chemistry pulled it off, and why "chiral synthesis," as it's called, is really just turtles all the way down.