The Picrosirius Red Solution is intended for use in the histological visualization of muscle and collagen fibers in tissue sections. The PSR stain may be viewed using standard light microscopy or polarized light resulting in birefringence of collagen fibers. Light Microscopy: Collagen:Red Muscle Fibers:Yellow Cytoplasm:Yellow Polarized Light Microscopy: Collagen:Yellow-Orange and Green Birefringence