National Institutes of Health

http://stemcells.nih.gov/info/basics/pages/basics1.aspx

 

Stem cells: What they are and what they do

http://www.mayoclinic.org/tests-procedures/stem-cell-transplant/in-depth/stem-cells/art-20048117

 

Basics of Stem Cell Research (AMA American Medical  Association)

http://www.ama-assn.org/ama/pub/physician-resources/medical-science/genetics-molecular-medicine/related-policy-topics/stem-cell-research/basics-stem-cell-research.page?