Fluorescence microscopy is ubiquitous these days. Open a life science journal, and you're bound to see photomicrographs in shades of red, yellow, green, and blue.
Most of this work involves intensity analysis, inferring the abundance of a protein or magnitude of an event from the strength of the color. But fluorescent labels generate two other types of signals, too. One is the lifetime of the fluorophore's excited state; the other is the wavelength of its emitted light.
Microscopists and microscope manufacturers have developed tools and techniques that allow researchers to probe these signals, enabling them to add depth and nuance to their studies. As a result, multiprotein associations can now be monitored, while autofluorescence worries are a thing of the past. But such improvements aren't cheap; lifetime-measuring equipment costs between €22,500 and €55,000, while spectral-imaging microscopes could cost $300,000 or more.
By measuring the time a fluorophore takes to decay ...
