What causes multicellular organisms to get larger?

Multicellular organisms grow larger primarily through two processes: cell division and cell enlargement. Cell division, especially through mitosis, allows for an increase in the number of cells, while cell enlargement occurs as cells accumulate more cytoplasm and organelles. Additionally, the coordination of these processes is regulated by genetic and hormonal factors, which ensure that growth is balanced and appropriate for the organism's needs. Environmental factors, such as nutrient availability, also play a critical role in supporting growth.