We asked skin experts the question we wonder every time we buy a new skin care product or add a step to our routine: In what order should I apply my skin care products, and does it matter? Turns out, it does!

So which product goes on top of what, you ask? An easy rule of thumb to follow is to apply your products with the thinnest consistency to thickest, or from liquid to cream. “In general, think thin-to-thick, but you also want to first use the products with the ingredients that are most important to penetrate into the skin (like antioxidants in serums) and finish with the products that need to sit on top of the skin (like emollients and humectants in moisturizers),” says Dr. Rogers.