Just when you think Olaplex cant get any better, they drop this one on us! Introducing No.0 intensive bond building hair treatment. In an ever changing world it is important to have salon quality treatments in the convenience of our home. That's where No.0 comes in, it can be used alone to repair or for best results use it as a primer to your No.3 treatment. Olaplex technology works best when the product is wet in the hair. No.0 is a watery liquid that will dry quickly. Using No.3 over it, keeps the hair damp so both products can continue to work during the process.