The Leica Fluorescent Dyes Overview is an informative digital resource provided by Leica Microsystems, offering a comprehensive introduction to the most commonly used fluorescent dyes in microscopy. This overview is essential for researchers aiming to visualize specific cellular components with high precision using fluorescence techniques. The resource details various types of fluorescent dyes, including widely used ones like Fluorescein Isothiocyanate (FITC) and Tetramethylrhodamine Isothiocyanate (TRITC), as well as the Alexa Fluor dye series. It explains their excitation and emission spectra, chemical properties, and how they can be coupled to antibodies or other biomolecules for specific labeling in immunofluorescence and flow cytometry applications. Beyond protein labeling, the overview covers the application of fluorescent dyes for detecting nucleic acids, glycans, and other cellular structures. It also discusses their utility in live cell imaging for visualizing organelles, tracking cellular processes, and performing functional assays, including the detection of non-biological substances such as calcium ions. This guide highlights the versatility of fluorescence microscopy, emphasizing the ability to use multiple fluorochromes simultaneously by selecting dyes with distinct excitation and emission wavelengths. This capability allows for multi-color imaging and complex co-localization studies, making it a powerful tool for diverse biological and analytical microscopy applications.