‘The structure of cells’ examines detailed cell structure. The plasma membrane is the cell's boundary structure and provides a barrier to other cells and the external environment. These membranes are an incredibly complicated and dynamic mixture of lipid (fat) molecules and proteins. The features of cell structure such as mitochondria, cytoplasm, organelles, endoplasmic reticulum, cilia, flagella, microtubules, and cytoskeleton are described. The principles of energy and heat generation, protein and lipid production, and the processes of phagocytosis and exocytosis are all explained. The history of cell structure discovery is provided along with descriptions of phase contrast microscopy and time-lapse microscopy used to view these structures.