Stems cells: cells that are capable of either differentiating into specialised cells or producing more stem cells.
Embryonic stem cells:
They are found in blastocysts (very early stage embryos). They can differentiate into all possible types of specialised cell (pluripotent).
Adult stem cells:
They are found in the developing foetus and onwards. They can only differentiate into certain types of specialised cell (multipotent). They are found specifically in:
Surface of the eye
Brain
Skin
Breasts
Testicles
Gut/intestines
Muscles
Bone marrow