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.
Moisturizers with Retin-A. You can apply moisturizer before or after Retin-A... This will not decrease the efficacy of the Retin-A. If you have a tendency to be dry I encourage you to apply your moisturizer before the Retin-A. Remember that Retin-A is only for night use. Hope this helps.