The Nucleus is the largest organelle in the cell and is a membrane bound organelle. The nucleus has a sphere like shape and is around 5 to 20 μm (micrometers). Found exclusively in eucharotic cells, the nucleus houses the cells DNA but it also has other functions, such as being the place for DNA and RNA synthesis and processing and even being highly involvd in the overall structure of the cell.
Left: Diagram of the nucleus • Right: (From Proyecto lab) Red Onion cells under a microscope (you can see the nucleus as a small dark dot)