What is the difference between Embryonic and Repair Stem Cells? Home Study Course "Stem Cells 101" coming right up! Embryonic Stem Cells have only one job! In a relatively short 9 months they build a human baby. That is a monumental task and these stem cells must rush to build everything from the nose on your face to the valves in your heart. This is why, originally, scientists believed that they held so much promise. But, embryonic researchers are starting to change their minds and saying that it JUST ISN’T WORKING. Don Margolis explains what the difference is between embryonic and Repair Stem Cells in Stem Cells 101 #3.