Skin is the largest organ in our body. The average weight varies depending on the individual, but it is about 3-4kg, which is 6-7% of body weight, and skin has an average area of 2m2. The skin is divided into epidermis, dermis and subcutaneous fat. The epidermis consists of four cell layers (stratum corneum, stratum granulosum, stratum spinosum, stratum basale) with an average thickness of 100µm. The cycle is about 52-75 days.The epidermis has keratinocytes, melanocytes, Langerhans cells, and Merkel cells and is involved in skin barrier, pigmentation, immunity, and sense of touch.The dermis is 1-4mm thick, divided into papillary and reticular dermis, supporting the epidermal layer, providing nutrients, and protecting from external damage. It also plays an important role in moisturizing the skin by regulating body temperature and storing moisture…

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