Clearly Corrective Dark Spot Solution by Kiehl is a fast-acting serum that evens skin tone and diminishes dark spots to impart overall radiance and luminosity to the skin. Activated C – a potent next-generation active in the serum, penetrates rapidly to attack deep-set dark spots while preventing the formation of new discolorations for visibly more uniform skin tone and clarity. White Birch Extract – a sugar derived ingredient and a potent active in the serum, increases skin elasticity levels and collagen production resulting in restored skin density, volume and thickness.