In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. Mitochondria are often described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of the chemical energy. In addition to supplying cellular energy, mitochondria are involved in a range of other processes, such as signalling, cellular differentiation, cell death, as well as the control of the cell cycle and cell growth. This book reviews research on the mitochondrial metabolism in age-related neurodegenerative disorders such as Alzheimer's and Parkinson's disease; mitochondria and ageing; apoptosis and peritoneal injury; diabetes, mitochondria and brain endothelium dysfunction as a dangerous triad for neurodegeneration.