Fluorescent Beads (Microspheres) are mondispered, polystyrene-based microspheres. The photostable fluorescent dyes are physically encapsulated in the microspheres, which prevents dye leaching and promotes stability for long periods of time under proper storage conditions. These green carboxyl fluorescent beads have sizes ranging from 167 nm to 500 nm and the desired density of carboxylic acid for targeted protein or ligand immobilization.