The human body is a big world of cells. These cells are not the same. According to statistics, there are more than 200 kinds of cells in the human body, and these cells perform their duties conscientiously. The red blood cells swimming in the blood are double concave disc-shaped, like a well-equipped submarine, carrying the necessary oxygen for life activities and delivering them to every cell of the body. The white blood cell is just like the loyal guard of the body's defense army. The octopus like tentacles on its surface are ready to entangle the invading enemies and devour them. Skeletal muscle cells like to attach to the trunk bone and limb bone. They are large and small, long and short, intertwined with each other like vines, which can stretch and contract. They form skeletal muscle fibers and give the human body strong strength. If more than 300 million muscle fibers in a person's whole body contract in one direction at the same time and work together, the power generated is equal to a crane!