Pregnant
Bone Marrow: one of the first and most well-known stem cell niches, bone marrow houses the majority of hematopoietic stem cells. Isolation of cells from this area is generally very invasive and requires anesthesia.
Peripheral Blood: in recent years, hematopoietic stem cells (HSCs) have increasingly been isolated in the blood. They can be mobilized from the bone marrow by cytokine treatment. Typically, HSCs are selected for CD34. This type of isolation is far less intrusive than bone marrow isolation.
Umbilical Cord Blood (UCB): typically discarded following birth, the umbilical cord was discovered to be rich in hematopoietic stem cells (HSCs). UCB provides lower amounts of HSCs and is usually reserved for treatment of children.
Amniotic Fluid: multipotent stem cells have been isolated from pregnant women.

Other Notable Niches: Brain, Skeletal Muscle, Skin, Teeth, Heart, Gastrointestinal Tract, Liver, Pancreas, Testes

References:

  1. Gavrilov, S. et al. 2009. Curr. Stem Cell. Res. and Ther.. 4:81.
  2. Weaver, C.H. et al. 2001. Bone Marrow Transplant.. 27: S23.