For a biologist interested in the mechanism of cell proliferation, the
most important event in the life of a cell was, until very recently,
cell division. As we mentioned, when a cell divides into two daughter
cells, it undergoes a process called mitosis; mitosis itself is
subdivided into four stages called prophase, metaphase, anaphase, and
telophase. Mitosis in most cells takes less than one hour. Between one
mitosis and the next, there can be an interval, from a few hours to
several days in length, during which a cell is said to be in interphase.
The entire period between the midpoints of two successive mitoses is
called the cell cycle.