In part 3, Professor Caplan discusses the science behind mesenchymal stem cells: sources of mesenchymal stem cells (MSCs), because all MSCs are pericytes one can find them in any tissue that has blood vessels, pericytes express markers of MSCs, frequency of pericytes in human tissue, most abundant source of pericytes is adipose (fat) tissue, adipose-derived stem cells, how MSCs are separated from fat, chemistries MSCs from different tissues are not the same, MSCs function at sites of injury, mesenchymal stem cell homing in mice, MSCs don’t make fat, they don’t make muscle. They come back as pericytes, and not all pericytes are MSCs.