The most important feature of a cell with a cell cycle is that it has a nucleus, which completes the cell cycle through mitosis of the nucleus. The cell cycle is the process by which cells divide, form one generation of daughter cells, and then re-form the next generation of daughter cells is called the cell cycle. In general, the cell cycle is completed through the replication and division of DNA in the cell, where DNA undergoes three phases: pre-DNA synthesis, DNA synthesis phase, and DNA division phase. In each of these phases, the cell with the cell cycle undergoes morphological changes, such as the formation of spindle filaments, the division of spindle filaments, and so on. Through a series of changes, a mother cell eventually divides into two daughter cells with identical morphology and function, and then these daughter cells go through the cell cycle and divide into two more identical daughter cells, and so on, which is the whole process of life.