Theory predicts that the movement of molecules along the surface of a cell is dominated by “hops,” with the molecules jumping in and out of the liquid surrounding the cell [1, 2]. Such a process, for example, is thought to occur when molecules transport cargoes from one region of the cell to another. But experimentally tracking the full 3D motion of such molecules is notoriously difficult, making it hard to confirm these predictions. Now, Daniel Schwartz from the University of Colorado Boulder and colleagues have done exactly that, capturing the 3D trajectories of human serum albumin molecules on silica surfaces submersed in a water-glycerol mixture . The team observed that the strength of the electrostatic interactions between the surface and the molecules strongly influence the characteristics of the hops, such as their length and duration. The research shows the potential of fluorescence imaging for tracking and probing the 3D motion of single molecules along a submersed surface. Such an ability could enable a deeper understanding of molecular processes in cells.To read more, click here.