The Fluo LED4000 and Fluo LED100 fluorescence microscopy illumination systems from Leica Microsystems GmbH are suitable for cell biology applications. The 4000 model offers users five freely combinable LED modules and specific excitation of fluorochromes with one wavelength. The company says that its stable excitation intensities yield better quantification and that its reduced stray light produces higher-contrast images. Most suitable for applications requiring one fluorochrome only, the 100 model delivers excitation at 470 nm. It is compatible with all microscopes equipped for fluorescence and, because it has no ballast, requires a minimum footprint.