Potency is the property of stem cells that determines their ability to self-renew and differentiate into diverse cell types. Totipotent stem cells include spores, zygotes, or cells of plant meristems that can develop into all types of cells to form a complete organism. Pluripotent stem cells or PSCs, such as embryonic stem cells, can form most but not all body cell types . Thus, they cannot form an entire organism independently. Genetically engineered somatic cells such as fibroblasts yield induced PSCs that can differentiate into any desired cell type. Adult stem cells are multipotent but can only produce all cells of a specific tissue type. For example, mesenchymal stem cells can produce osteoblasts, myocytes, adipocytes, and chondrocytes, but not neurons or blood cells. Multipotent stem cells can divide into oligopotent and unipotent cells that undergo fewer self-renewals and differentiate into closely related cell types. Myeloid progenitors are oligopotent and give rise to erythrocytes, phagocytes, or granulocytes, while the unipotent colony-forming unit-erythroid can only form erythrocytes.