I initially received this product as a free bonus item around the holidays and, since it wasn't part of my existing skincare routine, it sat under my bathroom sink for a while. After a couple months, I was back on Paula's Choice thinking I'd buy the C15 Booster for some dark spots I'd been noticing, but in meandering around the site, I looked up the ingredients in this product, realized it had a high vitamin C content, and decided to try it instead. I never exactly thought I had dull skin, but within a couple of weeks my skin had a nicer glow and radiance and was better hydrated. Those dark spots began to fade too. When I ran out, I switched to another free product I had received (line minimizer, which I don't believe is available anymore) -- and those great results began to fade over time. Now that I have used up that other product, I am back to the brightening essence for good, and even though I've only been back with it for a couple of weeks, I can already see and feel the difference again. I have maintained an advanced skincare routine for several years for my very sensitive skin, but adding this product to it has given my skin a boost that none of my other PC products have achieved. I definitely recommend trying it. It's a very thin liquid, so a little goes a long way, and I find a bottle of brightening essence lasts me much longer than other boosters or serums.