After removal of the loxP-flanked cassette via cre-mediated recombination, PA-GFP is expressed in all cells where Cre recombinase is expressed. PA-GFP::NLS is enriched in the nucleus, but can be also detected in the cytoplasm of neuronal cells. PA-GFP shows very weak fluorescence at 517nm when excited at 488nm before photoactivation. Upon photoactivation with light at ~400nm PA-GFP is converted into its fluorescent form. This form shows strong emission at 517nm when excited at 488nm and allows the conditional fluorescence labeling of individual, living cells which can be imaged using conventional GFP filter sets. Photoactivation can also be efficiently achieved using 2-photon excitation at ~750nm and imaged after photoconversion using excitation at ~950nm.