Cyclodextrin, a probe for studying adhesive interactions.  In this short communication, we introduce alpha-cyclodextrin as a new probe to study mechanisms of adhesive interactions. We show that this cyclic polysaccharide, that consisting of six glucosyl residues linked by alpha-1,4 bonds, was the only sugar of 22 tested that dramatically blocked a specific cellular interaction in the sea urchin embryo (p<0.001 compared with non-sugar controls). A total of 150-400 embryos were sampled for each concentration of each sugar tested. Mechanisms of cellular interactions have been studied for almost a century and they still remain poorly understood. Cyclodextrin is an exciting new tool that can be utilized for investigating these mechanisms.