Plant callus (plural calluses or calli) is a mass of unorganized parenchyma cells derived from plant tissue (explants) for use in biological research and biotechnology. In plant biology, callus cells are those cells that cover a plant wound. Callus formation is induced from plant tissues after surface sterilization and plating onto in vitro tissue culture medium. Plant growth regulators, such as auxins, cytokinins, and gibberellins, are supplemented into the medium to initiate callus formation or somatic embryogenesis.