Nioxin 3D Intensive Diamax Hair Thickening Treatment. A volumizing treatment for thinning hair. Increases the thickness of each existing hair strand to create body. Hair visibly looks thicker, fuller & more manageable. Fights against breakage to promote longer & healthier hair growth. Nioxin 3D Intensive Diamax Hair Thickening Treatment 3.38 oz. HOW TO USE. Apply a small amount of the hair thickening serum directly to your scalp. Gently massage the serum into your scalp using circular motions. Do not rinse out. For best results, use daily as part of your hair care routine.