Totipotent stem cells are one of the most important stem cells types because they have the potential to develop into any cell found in the human body. In human development, the egg cell in a woman and the sperm cell from a man fuse together to form a single cell called the zygote. The zygote divides numerous times and forms cells that are the precursors to the trillions of cells that will eventually constitute the human body.
It may sound rather complex and in a sense it is, when you consider that a simple cell has the potential to develop into a specialised one with a specific job in the body. It is simple, however, in that it's a clear sequence of events that begins with an egg cell and a sperm cell. The zygote from that fusion of an egg cell and a sperm cell then begins cell divisions that are capable of forming the entire human body. It is these cells that are totipotent, so called because their potential is 'total.'