Alexa Fluor® conjugates are highly photostable and remain fluorescent over a broad pH range. The excitation and emission maxima are nearly identical to those of FITC. However, Alexa Fluor® 488 tends to be brighter and more optimal for intracellular applications. Due to nearly identical excitation and emission properties but different spillover characteristics, FITC and Alexa Fluor® 488 cannot be used simultaneously. Alexa Fluor® 488 exhibits extraordinary photostability, which makes it highly suitable for fluorescence microscopy.