The nucleus is considered the headquarter of the cell because it is responsible for controlling all cell activities. The nucleus determines which proteins are to be made and retains the information for any proteins that the cell currently produces or has made previously. Additionally, the nucleus controls the functioning of cell growth, reproduction, and metabolism. Gene expression, DNA replication, and DNA repair also all take place in the nucleus. Essentially, the nucleus gives instructions telling the cell what and when to carry out a certain process.