The P{UAS-Brainbow} construct allows stochastic expression of one of multiple possible fluorescent proteins from a single transgene using P1cre mediated excision. P{UAS-Brainbow} contains UAS regulatory sequences followed by three different lox sites (lox2272, lox5171 and loxP) and a transcriptional stop sequence followed by genes encoding three cytoplasmic fluorescent proteins: EGFP tagged with Tag:V5, EBFP2 tagged with Tag:HA and mKO2 tagged with Tag:MYC. The transcriptional stop, EGFP and EBFP2 sequences are each followed by a different lox site (lox2272, lox5171 and loxP respectively). No expression occurs in the absence of P1cre recombinase, due to the presence of the transcriptional stop sequence. In the presence of P1cre, recombination occurs between one of the matched pairs of lox sites, removing the transcriptional stop sequence and resulting in the irreversible selection of one of the fluorescent proteins (the one that ends up being juxtaposed to the UAS sequences).