This is my second time purchasing this booster and I will likely always have it in ny retinol rotation per the very unique and elegant lightweight formulation. Finding actual light gel serums for my combo oily/blemish prone skin has never been easy among as an understatement with any active chemical exfoliant type product. There is much more on the market now than there was even a few years ago but annoying so many actives like retinol are made in endless overly moisturizing lotion/cream serum or night cream similar to how glycolic acid typically always had been prior to the wave of modern liquid exfoliant now. All those options will only breakout and congest blemish prone skin types so finding light formulas takes alot of trial. That is why I started out using retinol serums off Amazon years ago from many smaller unknown brands per the lower gentle percentage among many more light formulas having been available. I was ready to move up to a 1% last year among there being so few on the market with Paula's Choice having had this lightweight formula for my skin type and it just works. What I will never be happy about is the arrogance of the brand raising the prices extremely over the years since the company was bought out (big surprise and change from an affordable brand for the people) including this serum which is insanely overpriced at over $50 for a mere .5 oz so basically over $100 for 1 oz as all serums are sold from every brand and only at this high a price point typically when much more high end medical or dermatologist type lines among for more mature skin. On top of that to market this as a booster and advise people to mix it with other products is idiotic as at this price you want to not waste the product and get the full potency among your money's worth instead of diluting it frivelously. If you need to dilute it you rationally shouldn't be using this strong of a product or are using too often per being impatient. Many people want to jump into retinol fast and at highest strength like so many other actives as Vitamin C when it's simply not smart or needed. The highest and strongest is not the right choice for everyone and started with a smaller percentage then working up to higher if even truly needed prevents irritation and all the effects complained about every time. I added retinol serums into my routine simply for anti aging prevention and as a huge bonus that they keep my fussy skin clear among fade the occasional post blemish mark. They obviously are great for those with much more mature skin, damage, and pigmentation as are the only who ever need to worry about working up to max strength. Retinol actually builds up the longer you use it (similar to quality antioxidant serums but unlike bha/aha) and for many the strongest dose isnt needed. Within the last 6 months I've tried Retinal serums as well which surpass even Retinol as they are 11x more potent to comparable retinols per being a shorter conversion from pure retinoic acid but having much less if any sensitivity and adjustment of retinol serums which really impressed me. Per their formulas being much more advanced and expensive to create there are not many brands that have them outside of several medical grade lines to date and at higher costs as well. A new formula I adore that launched an amazing variety is Maelove but as they are indefinitely out of stock I am back to using this booster as my backup as much as the pricing kills me to pay because even with the good formula nothing from this brand justifies the price outside of them just taking advantage charging more for the higher percentage and a scentless light milky gel formula not many brands have. Regardless the strategic and well placed combination of Vitamin C, Niacinamide, Retinol/Retinal, and BHA Serums in my skincare routine has truly helped make my skin flawless in anti aging, clarity, brightening, deep cleaning pores etc. Chemical exfoliants do more than anything manual ever will without all the irritation of drying out your skin/stripping it as so many of us do in out teens when blemish prone not knowing any better. Combining these actives in between a gentle hydrating cleanser, moisturizer, and spf full of antioxidants, peptides etc is all the balance you need. Understanding ingredients and years of trials finally has left me content with my routine as much as I am always tempted to try occasional new released products per my love of skincare and quality formulas that advance by the year! 💕