:For human anatomy, see Islets of Langerhans An islet's a small island. Types As suggested by its origin as islette, an Old French diminutive of "isle", use of the term implies small size, but little attention's given to drawing an upper limit on its applicability. Rock: A "rock", in the sense of a type of islet,'s a landform composed of rock, lying offshore, uninhabited, and having at most minimal vegetation. Sandbar: An exposed sandbar's another type of islet. Sea stack: A thin, vertical lan… (More on Islets)