The nucleus is the largest organelle in an animal cell, while plastids are the largest organelles in plant cells. The nucleus is a membrane-bound structure that acts as the command center of the cell. It houses the cell’s hereditary information in the form of DNA (deoxyribonucleic acid), controls all cellular activities including growth, metabolism, and reproduction. The nucleus also contains the RNA (ribonucleic acid), which is housed in the nucleolus, a smaller structure occurring in the nucleus. RNA plays a role in transmitting orders from the DNA to the rest of the cell. It also serves as a template for protein synthesis.