Often your face and fingers twitch and your eyes move rapidly during

If this is a stages of sleep question, the answer might be REM which stands for Rapid Eye Movement. If not, please give more details.

Nucleus is the organelle that contains chromosomes

Cell division is important to single celled organisms because it allows the cells to reproduce. through cell division, cells make exact copies of themselves. when single celled organisms go through cell division, they make exact copies of themselves which is how they reproduce.