Orange II reagent, Pap 2B a solution of Orange II dye with added phosphotungstic acid (PTA). The first step in using the Papanicolaou staining method implies nuclear staining with a hematoxylin solution, and next two steps consist of contrast staining using the monochromatic OG-6 or Orange II reagents and one of the polychromatic EA reagent formulations consisting of two acid dyes, the Eosin Y and Light Green SF. The Orange II molecule stains the cytoplasm, and in later stages of the procedure it remains only in the mature, keratinized cells that turn different shades of orange. The third step consists of using of one of the polychromatic EA solutions that stains the unstained cellular components, such as squamous cells, nucleoli, cilia, and erythrocytes. Test samples can be gynecological and non-gynecological, such as sputum, urine, and cytological puncture samples. In order to obtain optimal staining results, BioGnost’s Orange II reagent, Pap 2B properties are completely in accordance with other BioGnost’s reagents used for cytological staining acc. to Papanicolaou – Hematoxylin HP, Pap 1A and 1B, EA 31 reagent, Pap 3A, and EA50 reagent, Pap 3B, as well as alternative counterstain polychromatic stains, such as EA 65 reagent, Pap 3C and 3D.