Details a placenta specific gene manipulation by transducing blastocysts with lentiviral vectors1. After a removal of zona pellucida which functions as a physical barrier, trophoblast cells lying outermost layer of blastocyst were transduced from outside with high-titer lentiviral vectors. As most placental cells descend from trophoblast cells while fetus originated from inner cell mass, transgene expression can be observed in trophoblast cells from preimplantation stages and in placenta...