After removing the subcutaneous fat and blood vessels from the skin with a scalpel, we floated the whole skin with an unsubmerged epidermis on trypsin solution (Gibco, 27250–018, USA) overnight at 4°C. The next day, we collected the epidermis by gently scraping it away from the dermis and repeatedly pipetted it until it was triturated.
Source: wiktionary