What causes fingers to look wrinkled after soaking in water?

On apex it say because "water enters the cells in the skin"

Our fingers wrinkled after soaking in because our fingers have thick layer of epidermal tissue. The outer layer of epidermal tissue is the stratum corneum which contains alternate layers of lipid and protein called keratin. keratin absorbs water when fingers are soaked in water. keratin swells but inside the fingers cells do not swell and fingers get wrinkled.