Mitosis takes place in the cells of eukaryotic organisms. The process starts in the cells nucleus with the DNA condensing, and the nuclear envelope or membrane breaking down to give the chromosomes room to move during the process instead of sticking to the envelope.
There are four phases, including prophase, where the condensing of the DNA occurs. During the second stage, metaphase, the chromosomes line up on the equator preparing for the splitting of the cells. The third stage, anaphase, is where the splitting actually occurs. During the last stage, called telophase, the two daughter cells develop their own nucleus envelope, the DNA spreads back out inside of it and the new cells are complete.