Matrix The area, beneath the proximal nail fold ,where stem cells modify skin cells into the cells of the nail plate.Related Articles: Understanding the Impact of Thumb Sucking on Nail GrowthUnderstanding Staple Nails and SolutionsNatural vs. Nourished: Is Bare Better for Your Nails?Understanding Nail Product Claims in the Beauty IndustryWhat causes the nail plate to turn black or darkly colored?