Assays performed in whole cells or intact tissue sections allow for monitoring a more complete set of biological parameters to a particular compound or drug target, and are thus considered “high-content” analyses. High-content analysis can be applied to all stages of the drug discovery process and is well suited to tracking the intracellular processing, localization, and movement of fluorescently labeled molecules such as proteins. It is possible to simultaneously monitor multiple targets, such as components of a signaling pathway of interest. In addition, monitoring the activity of membrane proteins and a cell’s electrophysiological response can provide information that standard high-throughput biochemical analysis simply cannot tackle. Single cells can be monitored, providing greater subtlety in the evaluation of the variability of the response to a particular drug or treatment. Light engines help here just as they do in microscopy with powerful, stable, robust, spectral pure light.