The callus is a disorganized mass of cells that grow in plants in response to various biotic and abiotic stimuli. Callus plays an important role in cell cultures in vitro, as a starting material for many subsequent studies such as single-cell culture, protoplast culture, micropropagation, etc. In this review, callus as well as the factors affecting callus formation and proliferation (plant growth regulator, mineral medium, carbon source, type of explant, light condition, callus line) are explored to provide a brief overview of callus culture