Mitochondria are critical organelles in the metabolic regulation of all eukaryotic organisms. Knowledge of their biochemistry and molecular biology in plants has been fuelled over recent years by the rapid progress made in genome sequencing and the ability to manipulate gene expression. At the site of oxidative energy metabolism they synthesise the majority of respiratory ATP in plants, animals and fungi. They are involved in the production of many novel compounds, such as phospholipids, nucleotides and several amino acids. Essential to eukaryotic life, organisms with the capability to respire anaerobically can only survive when mitochondria are present to manufacture these unique chemicals. This timely volume is an excellent companion edition to Plastids, also published in the Annual Plant Review Series.