Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human congenital abnormalities, but it is much broader than that, taking in other non-birth developmental stages, including puberty; and other non-human life forms, including plants. The related term developmental toxicity includes all manifestations of abnormal development by toxic substances. These may include growth retardation, delayed mental development or other congenital disorders without any structural malformations.