Implantation following placentation is a unique system for mammals to reproduce. The initial attachment of the embryo to the uterus occurs via the apical cell membranes of two epithelial cells, trophoblast of the blastocyst and surface epithelial cells of the endometrium. Analysis of the implantation at the molecular level has been a difficult problem in reproductive biology. Recently, a major break through was made in this area: A discovery of a novel cell adhesion molecule complex mediating the initial attachment of trophoblast to the endometrial epithelium. This review provides a brief overview of cell adhesion molecules involved in implantation and introduces identification and characterization of trophinin and tastin.