Green Fluorescence Protein Chromophores Meet the <i>M</i> <i>eta</i> ‐Amino Effect: Fluorescence Turn‐On and Beyond

Achieving fluorescence activation of green fluorescence protein (GFP) chromophores in solution under ambient conditions has been a long‐standing challenge in organic photochemistry. In this context, the meta‐ amino substituent effect, originally recognized for promoting fluorescence in stilbenes, has been identified as a powerful design principle for enhancing emissive properties of GFP chromophores. Beyond fluorescence turn‐on, m‐ amino‐substituted GFP chromophores exhibit distinctive photophysical characteristics, including pronounced solvatofluorochromism and atypical excited‐state deactivation pathways in both protic and polar aprotic solvents. These unique features have enabled their development as environmentally sensitive fluorescent probes and wash‐free cell‐imaging dyes. This review concisely summarizes key advances in this area over the past 2 decades.