A major advantage of this assay is that it can be conveniently multiplexed with other compatible assay chemistries to deliver more per-well information ( Fig. 1 ) [27] . This feature is particularly attractive for normalizing spectrallydistinct fluorescent or luminescent data sets such as genetic report assays [28] . Multiplex applications for viability and cytotoxicity will be handled in greater detail in a later section of this review. Lastly, although red-shifted from much of the problematic coumarin spectrum, the assay is susceptible to fluorescence interferences from test compounds [29] . Additional interferences should be expected from protease inhibitors or from color quenching chemical entities. 