The length of mitochondria is controlled by the equilibrium between fission and fusion rates. This balance is influenced by both internal factors (such as metabolic conditions and pathogenic factors within the mitochondria) and external factors from the cellular environment. When a cell has a low fusion-to-fission ratio, it results in the formation of many small, spherical or short rod-shaped mitochondria. Thus, shorter mitochondria are more likely to undergo fission, where they divide into smaller organelles. In contrast, longer mitochondria are more prone to undergo fusion, where multiple mitochondria merge to form elongated networks.