Step 1: Define the Problem

People who have Parkinson's disease experience difficulty with movement, balance and speech. These problems result from the death of specialized brain cells called dopamine neurons. These cells produce dopamine, a chemical that helps control muscle movements. The effects of the disease can be treated with drugs that help increase dopamine in the brain, but there is no known cure.

Researchers studying Parkinson's disease knew that the problem was to replace the dead dopamine neurons with healthy dopamine-producing cells.