In Microneedling, the pen is not enough to deliver results; you need a serum to play an active role in skin treatment. Several serums have been formulated, with each containing nutrient that seems beneficial to the skin. However, there are a few that are great to use; for instance, Kiehl's Midnight Recovery Concentrate is an excellent choice to use, as it contains skin lightening and collagen-stimulating formula. Also, they seem paraben-free, so it is easy to say that they are cruelty-free.