Abstract: Over the past 30 years, somatic embryogenesis induction and plant regeneration has been successful in many different cotton cultivars. However, the efficient conversion of callus into embryogenic callus is still a restricting step during cotton tissue culture and genetic transformation, because embryogenic callus induction is affected by many factors. This paper reviews the research into cotton embryogenic callus in terms of the origin, intrinsic and extrinsic factors affecting callus differentiation, as well as the techniques used to investigate the differential gene expression in the conversion process. We also discuss the problems encountered during the research.