Alexa Fluor 488 phalloidin is a high-affinity probe for F-actin that is made from a mushroom toxin conjugated with our bright, photostable, green-fluorescent Alexa Fluor 488 dye. Used at nanomolar concentrations, phallotoxins are convenient probes for labeling, identifying and quantitating F-actin in formaldehyde-fixed and permeabilized tissue sections, cell cultures or cell-free experiments.