 This study examined the spatial distribution of macromolecules on live cell membranes at the nanoscale. Using a combination of experiments and simulations, they discovered that they are sharp gradients in the concentration of macromolecules within a few nanometers of the membrane surface. These results suggest that certain regions of the membrane are more likely to exclude larger molecules such as glycoproteins and glycolipids, which could explain why some proteins are excluded from the membrane. This research provides insight into how plasma-membrane biophysical organization affects the binding of macromolecules, which could be used to improve the design of monoclonal antibodies. This article was authored by Daniel P. Arnold, Yashin Xu, and Shou-Shi Takatori.