Sometimes the absolute best way to try before you buy is with a small sample of the product. I have a drawer dedicated to beauty samples and i'm constantly collecting more.
Product samples can last from 1 to 2 days at most. When I make serum purchase, I keep them in their original boxes so I can refer back to the product descriptions as needed. By the way, I use serums twice a day... morning and night.
What are some of your favorite samples to use?