Inside a living cell, proteins and other molecules are often tightly packed together. These dense clusters can be difficult to image because the fluorescent labels used to make them visible can’t wedge themselves in between the molecules. MIT researchers have now developed a novel way to overcome this limitation and make those “invisible” molecules visible. Their technique allows them to “de-crowd” the molecules by expanding a cell or tissue sample before labeling the molecules, which makes the molecules more accessible to fluorescent tags. This method, which builds on a widely…