Every human cell is surrounded by a sugar coating known as the glycocalyx. It not only interacts with its environment but also reveals a great deal about cells’ internal states. Scientists at the Max Planck Institute for the Science of Light (MPL) have mapped sugar structures on cell surfaces using high-resolution microscopy. In initial studies, they were able to correlate the spatial arrangement of the sugar structures with specific physiological cell states. The results, recently published in Nature Nanotechnology, could pave the way for new diagnostic approaches, such as tumor detection.