An international research team, led by the University Medical Center Göttingen (UMG) in Germany, has developed a new method to distinguish fluorescent labels in cells based not on color but on the time it takes for a dye to emit light. This technique allows scientists to visualize up to eight different proteins in a single cell at once using standard microscopes. Their findings were recently published in the journal ACS Nano. Fluorescence microscopy is a widely used technique in biomedical research that lets scientists observe specific proteins and cellular structures. Researchers typically attach fluorescent dyes to antibodies that bind to the proteins they want to study. When light excites the dyes, they glow, and a microscope captures the emitted light. However, traditional microscopes can only detect three to four different colors at a time, limiting the number of proteins that can be studied simultaneously. The new approach, developed by Dr. Felipe Opazo and Dr. Roman Tsukanov, introduces an additional dimension to fluorescence labeling: fluorescence lifetime. This refers to the time a dye remains glowing after being excited by light, measured in billionths of a second. The researchers used a protein "pocket" that can be genetically modified into four different variants. Each variant creates a unique fluorescence lifetime for the dye inside it. This means that even if all dyes appear red in color, they can be distinguished based on their glow duration. To make the method practical, the researchers used nanobodies—small, specialized antibodies derived from alpacas. These nanobodies are much smaller than conventional antibodies and can easily bind to the protein pockets. Traditional antibodies are used to find specific proteins, while the nanobodies with fluorescent dyes reveal the location of these antibodies. This system allows for labeling multiple proteins in one step, using a preassembled combination of antibodies and nanobodies. The method, called NanoFLex, has significant practical benefits, especially in clinical research. Human tissues often have a natural glow that can interfere with traditional staining methods. However, the new technique can distinguish this background glow from the actual signals based on the different fluorescence lifetimes. This makes it particularly useful for analyzing limited biopsy samples. The researchers believe the number of detectable proteins could increase further with the development of new dyes and better data analysis techniques.