What are stem cells, and why are they so important? Stem cells are the builders and the repairmen of the world’s most complex construction project: the creation of a human body! Thanks to the seven million California voters who voted Yes on Proposition 71, California’s $3 billion stem cell initiative, California’s scientists are already making remarkable progress toward developing stem cell therapies for patients suffering from diseases long considered to be incurable. The road to therapies and cures is long and challenging; however, even the inevitable challenges and setbacks will help to advance our understanding of disease and injury. Find out what stem cells are, where they come from, how they are used in medicine today, and what promise they hold for medicine tomorrow.