Note that each Skin Nutritional Requirement directly targets one of the barriers, but the entire system is interconnected. That means addressing each requirement also helps indirectly address the others. It also means that one is not more important than the others. The order in which they are presented matches the regimen usage order, where each step of the regimen addresses certain requirements: Purify with cleanser, Balance with toner, and Rebuild, Moisturize and Protect with eye and face moisturizers.