A thing or an event that provokes a specific functional response in an organ or tissue of an organism is called as stimulus. It can be anything like heat, light, water, chemical et cetera. Any stimulus when encountered by the organism produces response in reference with the stimulus generated by the external environment or other organism.
Answer: Differentiation is the process by which unspecialized cells become specialized to carry out distinct functions. A stem cell is an unspecialized cell that can divide without limit as needed and can, under specific conditions, differentiate into specialized cells.
