Multi-spectral Microscopic Beads (IMAGE) National Physical Laboratory Caption The image is a mixture of microscopic fluorescent beads of different colors, mounted on a microscope slide and illuminated using a 488 nm, 40 mW Coherent Sapphire laser. This is a simultaneous two-color fluorescence image produced using Förster Resonance Energy Transfer (FRET) and the Image Replication Imaging Spectrometer (IRIS). FRET is used to measure distances, detect interactions and monitor conformational changes in biomolecules. Simultaneous imaging in several wavebands is essential to make measurements of a dynamic system, but this is difficult to achieve with conventional imaging techniques. However by combining FRET with the IRIS system, it has been demonstrated that it is possible to make measurements in four wavebands simultaneously, even at the low intensity levels associated with these measurements. Credit Agnieszka Bialek, National Physical Laboratory Usage Restrictions Crown Copyright, Credited to the National Physical Laboratory License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.