What it is: A treatment that primes your hair for deeper repair while rebuilding hair bonds, strengthening and protecting.

Who it's for: All hair types.

What it does: Though this treatment can be used on its own, it is specifically designed to work as a two-part system with the brand's No. 3 Hair Perfector (sold separately) to help strengthen and repair damaged hair. Redesigned for a quick, targeted stream application, it features an easy-to-use nozzle that primes the hair and delivers the highest concentration of patented bond-building technology of any Olaplex at home product.

How to use: Apply slowly to dry hair, distributing evenly from root to tip. Work into small sections by squeezing the liquid into the hair to be fully absorbed as you go. Hair should be damp, not drenched. Let it process for 10 minutes. Do not rinse. For a complete treatment, apply No. 3 Hair Perfector (sold separately) over your hair with No. 0 applied to it, combing through as needed. Let process for a minimum of 10 minutes. Rinse, shampoo and condition.