 He made a major transition in research direction in 2003 and began to emphasize the use of pluripotent stem cells to study emergence and differentiation of trophoblast.His group has also made contributions to the culture of such cells, and particularly the importance of low oxygen atmospheres to control differentiation.His was among the first laboratories to describe the generation of induced pluripotent stem cells from an ungulate species, the pig, and has recently been generating iPS cell lines from human umbilical cords to study preeclampsia.