GFP	green fluorescent protein
FRET	Förster resonance energy transfer
RFP	red fluorescent protein
GECO	genetically encoded calcium indicator for optical imaging
GECI	genetically encoded calcium indicator
ESPT	excited-state proton transfer
HOMO	highest occupied molecular orbital
LUMO	lowest unoccupied molecular orbital
fs-TA	femtosecond transient absorption
ESA	excited-state absorption
SE	stimulated emission
HGSA	hot ground state absorption
DADS	decay-associated difference spectra
EADS	evolution-associated difference spectra
p-HBDI	4′-hydroxybenzylidene-1,2-dimethyl-imidazolinone
DFT	density functional theory
TD-DFT	time-dependent DFT
MD	molecular dynamics