Cells have tiny structures inside of them called organelles. Organelles are very similar to human organs in that they help perform specific functions. However, cells don't have organelles called "the liver" or "the heart." Some of the names of cell organelles include the mitochondria, lysosomes, and the endoplasmic reticulum. Don't get scared by the strange names; Chapter Three focuses on cell organelles so that you can understand them completely.