Since scientists realized there is a type of cell that can grow into any other type, they have worked to use them to heal human conditions like Parkinson's and immune disorders. But because stem cells often come from embryos they remain controversial.
Learn more about advertising on the HowStuffWorks podcasts at www.howstuffworks.com/advertisers.htm
And to learn about your ad choices when listening to podcasts, visit
https://www.howstuffworks.com/privacy.htm#ad-choices
