Retinol has been one of the biggest beauty buzzwords of the past two years or so, but with so much choice and so many confusing messages about what the product actually does and how it should be used, it can feel like a bit of a scary ingredient. Luckily, if you’re unsure where to start, America’s bestselling retinol serum is also available in the UK, and it’s recently been reformulated to make it even better.