the Q: does it really matter if you apply moisturizer before serum? Or if your SPF goes on last?
 
the A: YES. layering incorrectly can prevent products from working properly and render them ineffective. for example, applying a cream before a serum would create a barrier, not allowing the serum to penetrate into the skin. the rule of thumb is to always apply thinnest to thickest *remember to save you active ingredients (i.e. retinol, AHAs, BHAs, etc) for nighttime* if you use an oil, always save it for last as they create a barrier on top of the skin to seal & lock in ingredients