There are 2 Key classifications for stem cells: embryonic stem cells and adult stem cells. Embryonic stem cells are taken from unused embryos resulting from in vitro fertilization which were donated to science. Embryonic stem cells can differentiate into any type of cell, or are thought of pluripotent. Grownup stem http://troytsole.designi1.com/19930033/the-definitive-guide-to-stem-cell-regeneration-for-knees