The adhesion of cells to the endothelium occurs through spatio-temporally regulated interactions that are mediated by multiple intra- and inter-cellular components. The mechanism of cell adhesion has been investigated primarily using ensemble-based experiments, which provides indirect information about how individual molecules work in such a complex system. In this project, we develop microfluidics-based in-vitro live-cell single-molecule fluorescence imaging technique to unravel nanoscopic spatiotemporal interaction between adhesion molecules during the cell migration. Specifically, we aim to address some key questions in the initial step of hematopoietic stem cell homing mediated by selectin-ligand interactions.