The interplay between carbohydrates, lipids, and proteins determines the stability and flexibility as well as the adhesive and responsive features of the surfaces of all cells. The molecular understanding of the interactions among and between the different classes of these biomolecules is rudimentary at best, a lack of suitable experimental methods being the major reason. Here we discuss a new approach for the specific labeling of fusion proteins of carrier proteins with synthetic compounds on cell surfaces and describe how this approach can be used to investigate the properties of the labeled molecules.