What is a stem cell?

Stem cells are the main cell types that can differentiate into mitosis-specialized cell types and have the ability to regenerate themselves to produce more stem cells, forming the tissues and organs of all multicellular organisms.

Mammals have two common types of stem cells; embryonic stem cells that can be obtained from the inner layer of the blastocyst stage and adult stem cells in various tissues.

Stem and progenitor cells in adults have the ability to repair the body and renew adult tissues. In a developing embryo, stem cells can differentiate all specialized cells — ectoderm, mesoderm, endoderm — (see pluripotent cells) as well as sustain the renewal of organs such as blood, skin, digestive organs.