obagi, Nu-Derm Tretinion Gel; $64

While we've all heard of the common vitamin A derivatives retinol and Retin A, most of us haven't heard of tretinoin (also known as retinoic acid). In a nutshell, Retinol and Retin A are a milder version of tretinoin. They do their job but most come in very small doses. Plus the skin then has to convert them into tretinoin so it can use it properly. So, it is much easier to get straight up tretinoin for the best anti-aging benefits. Tretinoin is also used to treat acne so it's perfect for those with oily skin. The product is incredibly strong so be sure to test your skin first before you slather on.