Natural moisturizing factor (NMF) is a collection of water-soluble compounds that are only found in the stratum corneum. These compounds compose approximately 20-30% of the dry weight of the corneocyte. NMF components absorb water from the atmosphere and combine it with their own water content allowing the outermost layers of the stratum corneum to stay hydrated despite exposure to the elements. Because NMF components are water soluble, they are easily leached from the cells with water contact - which is why repeated contact with water actually makes the skin drier. The lipid layer surrounding the corneocyte helps seal the corneocyte to prevent loss of NMF.