Within the human body, about 37.2 trillion cells are active 24 hours a day, 365 days a year. The cheery and rather airheaded Sekkekkyuu AE3803 is fresh out of training and eager to take on the vital mission of carrying oxygen. As is customary, Hakkekkyuu U-1146 is hard at work monitoring and removing alien germs attempting to establish a new home in the body. Little platelets are lined up for a fresh development project elsewhere. Cells' everyday lives are usually stressful as they work together to keep the body healthy, dealing with wounds and allergies, getting lost on their way to the lungs, and squabbling with similar cell kinds!