Us Weekly has affiliate partnerships. We receive compensation when you click on a link and make a purchase. Learn more! If I’ve learned one thing over my career as a beauty writer, it’s that vitamin C is the key to a luminous complexion.

You can find the ingredient in an array of formulations, from face moisturizers and eye creams to potent serums — and I’ve tried my fair share of all three. I’d say I’ve tested well over two dozen vitamin C serums in my lifetime, yet only one sticks out for its ability to boost my complexion’s natural radiance both immediately and over time: The Sunday Riley C.E.

O. 15% Vitamin C Brightening Serum. Get the Sunday Riley C.

E.O. 15% Vitamin C Brightening Serum at Amazon! It takes a lot for a skincare product to wow me, especially since I have pretty clear, unproblematic skin.

However, my complexion does lean a little dry. While vitamin C serums aren’t known for their hydrating capabilities, this one is so well-rounded that it manages to brighten, hydrate, diminish dark spots and firm the skin . As someone who tends to use an excessive amount of skincare, this formula not only gave me significant results, it also curbed my overconsumption.

So, how does this serum manage to do it all? It all comes down to the expertly-crafted formula that utilizes 15% THD ascorbate (the most stable form of vitamin C), saccharide isomerate extract which gently smooths the skin and a phytosterols complex that’s derived from soybeans and calms the sk.