Assays performed in whole cells or intact tissue sections allow for monitoring wide range of cellular responses to a particular compound or drug target, and are thus considered “high-content” analyses (HCA) or “high-content” screening (HCS). High-content analysis can be applied to all stages of the drug discovery process and is particularly valuable for assessing off-target activity of drug candidates. Using multiplexed fluorescent labeling, it is possible to simultaneously monitor multiple targets, such as components of a signaling pathway of interest. Monitoring the expression and translocation of proteins and other spatially-defined cellular characteristics provides information that conventional biochemical analysis cannot. Particular advantages of high-performance Lumencor Light Engines in these screening applications based on fluorescence microscopy are: (1) Broad spectral content — providing excitation for multiple fluorophores addressed to multiple cellular targets. (2) Output stability — ensuring consistent data quality across thousands of samples. (3) Electronic control — required for automation of large-scale multiplexed assays.