As with other areas of biological research, the progress that has been made over the past 25 years in the field of cell adhesion is impressive. In the late 1970s, the searchfor specific cell surface receptors for adhesion processes was initiated - ing mainly biochemical and immunological approaches. Since then, theint- duction of novel methods of cellular and molecular biology and powerful te- niques for manipulatinggene expression in transgenic and knock-out mice have greatlyadvanced the field. Not only dowe now know the precise molecular structure of many of thecell adhesion receptors that...