Which of the following stem cells has the narrowest differentiation potential?
Differentiation potential hierarchy is conventionally ordered conceptually from broadest to narrowest developmental outcome: totipotent covering entire organism plus supportive extraembryonic membranes, pluripotent covering all embryonic germ layers ectoderm mesoderm endoderm, multipotent covering multiple related types within a tissue system like blood, oligopotent covering few types, and unipotent covering single type such as muscle satellite cell generating myocyte or spermatogonial stem cell generating spermatozoon while still retaining long-term self-renewal capacity. Hence unipotent cells exhibit most restricted fate scope, although they remain bona fide stem cells due to maintenance capability and transplantation reconstitution ability over lifetime.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Unipotent narrowest differentiation potential hierarchy definition.