There are two main types of cells: eukaryotic and prokaryotic. All cells have three main parts - a cell membrane, cytoplasm, and nucleus. Animal cells contain additional structures like mitochondria, the Golgi apparatus, and endoplasmic reticulum. Plant cells have a cell wall and chloroplasts. Cells specialize to perform specific functions like photosynthesis in leaf cells, absorbing water and minerals in root hair cells, and movement via tails in sperm cells. Cells combine to form tissues, organs, and organ systems that work together in the body.