Embryonic stem cells
Human Embryonic Stem Cells (hESC) are a unique type of stem cell that is found for a short period of time following fertilization in a human embryo. Stem cells have two basic traits: 1) the ability to make an identical copy of themselves (replicative proliferation); 2) the ability to change or “differentiate” into different types of mature cells that make up a human body. hESC are unique in that they are “pluripotent” meaning that they have the ability to produce every cell in the human body and they have unlimited replicative proliferation potential. Stem cells found in a developed organism (so called “adult stem cells) can become a limited number of cell types (are not pluripotent) and generally have limited replicative proliferation capacities.