I urge everyone to bookmark that blog; it is always a fascinating tour of the weirder and wonderfuller places on our planet. And let me leave you with this simply jaw-dropping video of undulatus asperatus in action.
(A sunscreen with a physical block like titanium dioxide or zinc oxide can be applied last, after a serum or moisturizer.) Apply a serum next and, finally, moisturizer if you need it. Polis also recommends serums or sunscreens with moisturizers built in because they save time.
You apply the serum after your toner and before your moisturizer. A moisturizer has larger molecules than a serum. This means that a moisturizer will not penetrate the skin as far as a serum will. While serums deposit nutrients, moisturizers are meant to deposit moisture and hydration your skin.