Phagocytosis is a process by which certain cells, such as white blood cells and macrophages, engulf and digest microorganisms, cellular debris, and other foreign particles. This process is important for the body’s immune system to help protect against infection and other diseases. When a cell detects an invading particle, it extends its plasma membrane to envelop the particle and forms a phagosome. The phagosome then fuses with lysosomes, which contain enzymes and acids, to form a phagolysosome. The particle is then digested and the nutrients carried from the phagolysosome back into the cell for use. Phagocytosis is a crucial defense mechanism for the body and helps to protect against many diseases.