When human skin is injured, the wound-healing process is immediately initiated. If the injury is sustained during the fetal period in late pregnancy, the tissue regenerates without leaving a scar. By contrast, if the injury occurs after birth, the tissue repair results in scar formation. This is particularly true if the injury extends beyond the basement membrane into the deep dermis: this is because the dermal gap becomes filled with fibrotic collagenous tissue that disrupts the original tissue structure [1]. In some cases, the genetic, systemic, and/or local characteristics (e.g. strong skin tension) of the individual patient can amplify this fibrotic wound-healing response and lead to pathologically growing scars called hypertrophic scars and keloids [2]. Indeed, as shown by Fig. 11.1, a common cause of these scars is burns that involve the deep dermis. By contrast, superficial burns generally lead to mature scars.