Peroxisomes are ubiquitous, subcellular organelles in eukaryotes. They consist of a surrounding membrane to separate them from the cytosol (the internal fluid of the cell). Peroxisomes were discovered by Christian de Duve in 1965. Unlike lysosomes, peroxisomes are not formed in the Golgi apparatus, but are self-replicating by division.
One of the main functions of peroxisomes is to detoxify the cell by breaking apart hydrogen peroxide. They contain the enzyme catalase. Catalase can convert H2O2 (hydrogen peroxide, a toxic byproduct of cell metabolism) to H2O and O2, with 4H2O2 => 4H2O + 2O2.
Peroxisomes also catalyze the first two steps in the synthesis of ether phospholipids, which are later used to built membranes. In humans, peroxisomes are also responsible for oxidation of long fatty acids. Peroxisomes also contain other oxidative enzymes such as D-amino acid oxidase and urease oxidase.