This is a human induced pluripotent stem (iPS) cell. It was a skin cell that was reprogrammed to become an undifferentiated cell that now the potential to become any one of the 200 cells types in our bodies. This ability to become multiple other cells is called pluripotency. The purple stain in this image indicates that the active protein (enzyme) that is indicative of pluripotency is present and active within the undifferentiated cell. This is one of the first tests scientist perform to determine whether a cell is pluripotent.