A form of reproduction where an egg develops without the fusion of sperm with the egg cell. Parthenogenesis occurs commonly among insects and other arthropods. Artificially inducing parthenogenesis with human eggs may be a means to isolate stem cells from an embryo, without fertilization.

The description of the characteristics of a cell, a tissue or an animal; as black and white fur of a mouse are two phenotypes that can be found. The phenotype is determined by the genes (or the genotype) and by the environment. For example, short stature is a phenotype that can be genetically determined (and therefore inherited from the parents), but can also be caused by malnourishment during childhood (and therefore be caused by the environment).

A round of cell growth and proliferation in cell culture.

The ability of stem cells from one adult tissue to generate the differentiated cell types of another tissue.

Ability of a single stem cell to develop into many different cell types of the body.

Implanted embryos in the early stages of development until the establishment of the body plan of a developed organism with identifiable tissues and organs.

Fertilized eggs (zygotes) and all of the developmental stages up to, but not beyond, the blastocyst stage.

A progenitor cell, often confused with stem cell, is an early descendant of a stem cell that can only differentiate, but it cannot renew itself anymore. In contrast, a stem cell can renew itself (make more stem cells by cell division) or it can differentiate (divide and with each cell division evolve more and more into different types of cells). A progenitor cell is often more limited in the kinds of cells it can become than a stem cell. In scientific terms, it is said that progenitor cells are more differentiated than stem cells.

Expansion of a population of cells by the continuous division of single cells into two identical daughter cells.