The organelle known as the "control center" of the cell is the nucleus. It houses the cell's genetic material, DNA, which contains the instructions for all cellular activities and functions. The nucleus is surrounded by a double membrane called the nuclear envelope, which helps regulate the movement of substances in and out of the nucleus. Additionally, the nucleolus, found within the nucleus, plays a crucial role in ribosome production. Overall, the nucleus is vital for maintaining cellular function and integrity.