In order to understand in vitro meat, one must have a quick primer on stem cell biology.  A stem cell is a cell defined by its ability to self-renew or differentiate (change) into another cell type.  There are many types of stem cells, defined by their potency or ability to differentiate into other cell types [14].  For instance, a totipotent stem cell is a stem cell that can differentiate into any cell type of the body, including cells of the trophoblast which make up the extra-embryonic tissues collectively known as the placenta.  Totipotent stem cells only exist roughly up until the 8 or 16 cell stage of development.  Embryonic stem cells and induced pluripotent stem cells (iPSCs) are cells that can differentiate into cells of all 3 germ layers (ectoderm, mesoderm, and endoderm) and are commonly used in academic research to study development and disease as well as in therapeutic regenerative medicine. Multipotent stem cells are progenitor cell types which can differentiate into a limited number of cell types, usually but not always within a single germ layer. Together, these cells are commonly referred to as “adult” stem cells and are the type most commonly used in current stem cell therapies.  Much of the biology concerning in vitro meat will be derived from what we know based on development as well as iPSCs and adult stem cells.