MIT biologists have answered an important biological question: Why do cells control their size? Cells of the same type are strikingly uniform in size, while cell size differs between different cell types. This raises the question of whether cell size is important for cellular physiology. The new study suggests that cellular enlargement drives a decline in function of stem cells. The researchers found that blood stem cells, which are among the smallest cells in the body, lose their ability to perform their normal function — replenishing the body’s blood cells —…