CHIR99021 is a selective inhibitor of glycogen synthase kinase 3. CHIR99021 has been used to propagate mouse embryonic stem cells in 2i or 3i culture and is used to derive and propagate extended pluripotent stem (EPS) cell culture for mouse, human and pig. CHIR99021 can also be used for expansion of human naïve pluripotent cells containing the genetic pluripotency reporter OCT4-ΔPE-GFP+.