The Colibri, an LED light source for fluorescence microscopy, has been introduced by Carl Zeiss MicroImaging GmbH. The narrow-band LEDs replace conventional white light sources to produce high-contrast images with a suitable signal-to-noise ratio, enabling the detection of weak signals and fine details in applications ranging from routine biomedical research to complex live-cell imaging. The intensity of the LED can be set accurately for any wavelength and specifically adapted to the specimen. With the device, it is possible to switch excitation wavelengths in microseconds. A selection of four LEDs can be used individually, sequentially or simultaneously with any intensity setting. Ten wavelengths, from the UV to dark red, are available.