Dermatologists are medically trained to diagnose and treat illnesses of skin, hair, nails, and mucous membranes, including skin cancer, acne, and hair loss. These doctors perform a range of cosmetic and medical procedures for patients of all ages and genders. Such procedures could be biopsies, skin grafts, laser surgery, injections, or cryotherapy. To become a dermatologist, you must complete a three year residency training program after medical school. There are opportunities to subspecialize in dermatopathology and pediatric dermatology.