SkinCeuticals on Instagram: "To show that a vitamin C serum is still effective no matter the color over time, our Director of SkinCeuticals in Research and Innovation, Maggie Su, performed the apple test. As you’ll see, one apple has our C E Ferulic, vitamin C serum on it that has a clear color and the other has our C E Ferulic, vitamin C serum with a more amber color. Both C E Ferulic apples still look fresh and protect the apple from oxidation. No matter the serum, you can always expect the hi