Humans are complex biological robots that are made up of trillion of cells, each with their own structure and function. Even a single cell cannot slack off. Scientists have come a long way in estimating the number of cells in the average human body. According to the most recent estimates, the number of cells in a human body is around 30 trillion. Hataraku Saibou Black is about a fight of these 30 trillion cells against the bad habits of the owner of the body to keep him alive.