In what organelle does mitosis occur?

Yes mitochondria are organelles in the cytoplasm of cells. Their function is to make the energy for a cell.

actually, the mithochondrion (plural mitochondia) is an organelle in both, plant and animal cell, its job is to oxidise biological fuels, such as, liquids, protiens, and fats. so basically its the energy source of the cell. its size is about .5 micrometers. and it was discovered my many of scientists in the late 18 hundreds.