Elite PAP pen is a special marking pen that provides a thin film-like green-tinged hydrophobic barrier when a circle is drawn around a specimen on a slide. This water repellent barrier keeps staining reagents localized on the tissue sections, prevents mixing of reagents when differentially staining two sections on the same slide, and allows use of less reagents per section. Insoluble in alcohol and acetone, PAP Pen markings can be optionally removed with xylene after the staining procedure is complete.