Animation of a flight through a eukaryotic cell from an animal. Eukaryotic cells are the building blocks of all animals, plants and fungi. They are distinguished from prokaryotic cells (such as bacterial cells) by the presence of a nucleus (pink) containing the cell's genetic material. They also contain other organelles, including mitochondria (red and orange), which produce energy for the cell. Surrounding the nucleus is the endoplasmic reticulum (red), studded with protein-making ribosomes (yellow). Layered Golgi apparatus is yellow, and the paired centrosome is brown.