Certain parts of the brain govern specific functions. For example, the cerebellum is involved with coordination; the hippocampus with memory. Nerve cells (neurons) are the basic unit of communication in the brain.
Eukaryotic organisms use mitosis to reproduce sexually. In mitosis, the parent cell is divided into two daughter cells which be identical to the parent cell. Edit
Simple organisms may be unicellular, consisting of just one cell, while more complex organisms are multicellular. There are two types of cell division. Mitosis is used for growth and repair and produces diploid cells identical to each other and the parent cell. Meiosis is used for sexual reproduction and produces haploid cells different to each other and the parent cell. Unicellular vs multicellular An ameoba, a simple unicellular organism