Blood cells are the cells found in blood that perform essential functions for the body. There are three main types: red blood cells, white blood cells, and platelets. Red blood cells carry oxygen from the lungs to the rest of the body, while white blood cells are part of the immune system, helping to fight infections. Platelets play a crucial role in blood clotting, preventing excessive bleeding when injuries occur. These cells are produced in the bone marrow and have different lifespans and functions. Red blood cells typically live for about 120 days, while white blood cells can live from days to years, depending on their type. Maintaining a healthy balance of these cells is vital for overall health and well-being.