Tien received his M.D. from Johns Hopkins before training at Columbia University for his medicine residency and University of Pennsylvania for his pulmonary/critical care fellowship. He completed his postdoctoral fellowship in the Department of Cell and Developmental Biology at Penn with Ed Morrisey, where he defined cellular feedback loops critical to establishing the mesenchymal progenitor niche during embryonic development and postnatal maintenance. Tien established his own lab at UCSF in 2015, and his group is exploring the nexus between development and aging to build new framework in the study of tissue regeneration.