The Ordinary Niacinamide 10% + Zinc 1%

A $6 serum that outsells products 20 times its price. The Ordinary's clinical, no-nonsense approach to skincare — single-ingredient formulas at cost-plus pricing — made it the most disruptive beauty brand of the 2020s. This niacinamide serum visibly reduces pores and oil production within weeks, and TikTok's "skincare is science" movement made it a gateway drug to ingredient literacy.