Mitochondria are highly dynamic organelles that undergo coordinated cycles of fission and fusion to maintain their shape, distribution, and size. These dynamic processes are crucial for cellular functions such as cell cycle, immunity, apoptosis, and mitochondrial quality control. Mutations in core machinery components and defects in mitochondrial dynamics are linked to various human diseases. The main regulators of these processes are large GTPases from the Dynamin family. Mitochondrial fission involves the division of one mitochondrion into two, regulated by Drp1 and adaptors. Fusion is mediated by mitofusins (Mfn1, Mfn2) and optic atrophy 1 (OPA1), which facilitate outer and inner membrane fusion. Post-translational modifications and lipid composition also influence these processes. Understanding mitochondrial dynamics is essential for deciphering their function and the molecular basis of diseases. This review summarizes the molecular mechanisms governing mitochondrial fission and fusion in mammals, highlighting the roles of key proteins, their interactions, and regulatory factors. It also discusses the clinical implications of mutations in these proteins, linking them to various diseases. The review emphasizes the importance of mitochondrial dynamics in cellular homeostasis and the need for further research to fully understand these processes.Mitochondria are highly dynamic organelles that undergo coordinated cycles of fission and fusion to maintain their shape, distribution, and size. These dynamic processes are crucial for cellular functions such as cell cycle, immunity, apoptosis, and mitochondrial quality control. Mutations in core machinery components and defects in mitochondrial dynamics are linked to various human diseases. The main regulators of these processes are large GTPases from the Dynamin family. Mitochondrial fission involves the division of one mitochondrion into two, regulated by Drp1 and adaptors. Fusion is mediated by mitofusins (Mfn1, Mfn2) and optic atrophy 1 (OPA1), which facilitate outer and inner membrane fusion. Post-translational modifications and lipid composition also influence these processes. Understanding mitochondrial dynamics is essential for deciphering their function and the molecular basis of diseases. This review summarizes the molecular mechanisms governing mitochondrial fission and fusion in mammals, highlighting the roles of key proteins, their interactions, and regulatory factors. It also discusses the clinical implications of mutations in these proteins, linking them to various diseases. The review emphasizes the importance of mitochondrial dynamics in cellular homeostasis and the need for further research to fully understand these processes.