Human embryonic stem cells: Lessons from stem cell niches in vivo Sean C Bendall 1,2 , Morag H Stewart 1 , Mickie Bhatia 1,3 1 McMaster Stem Cell and Cancer Research Institute, Michael G. DeGroote School of Medicine, and Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada, L8N 3Z5. 2 Don Rix Protein Identification Facility, Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada, N6A 5C1; Keywords: human embryonic stem cells, hESC, hdF, niche, differentiation, embroid body, self-renewal, pluripotency, microenvironment, regenerative medicine, cell-based therapy. 3 Correspondence should be addressed to: Dr. Mickie Bhatia McMaster Stem Cell and Cancer Research Institute (SCC-RI) Michael G. DeGroote School of Medicine, McMaster University 1200 Main Street West, MDCL 5029 Hamilton, Ontario, Canada, L8N 3Z5 Phone: (905) 525-9140, x28687 Email: mbhatia@mcmaster.ca Acknowledgements: S.C.B. and M.H.S are supported by CIHR Canada Graduate Scholarship doctoral awards, M.Bhatia by the Canadian Chair Program who holds the Canada Research Chair in human stem cell biology and Michael G. DeGroote Chair in Stem Cell Biology.