Skin Cells that Stop Replicating During Wound Healing

Eligibility Details: - INCLUSION CRITERIA: - Age 20 - 39 years or age 70 years and older - Healthy (see exclusion criteria below) - Are able to understand the study risks and procedures, and consent to participate in the study. - Are able to read and speak English. - Caucasian or Africian American - Previous enrolled participants. EXCLUSION CRITERIA (SCREENING VISIT): - A medical condition that requires the use of chronic anticoagulant medication use such as warfarin, clopidogrel, heparin or antiplatelet agents other than low dose aspirin (81mg). - History of increased bleeding due to either a known medical condition or an undiagnosed cause. - A medical condition that causes impaired wound healing such as diabetes. - Current androgenic/anabolic and/or corticosteroid use or use within 90 days of the procedure (ocular corticosteroid use okay). - Current antibiotic or anti-viral use or use within 60 days of the procedure. - Active infections or chronic skin conditions that would prevent access to the biopsy area. - Taking non-steroidal anti-inflammatory agents (NSAIDs) such as Motrin (Ibuprofen), Advil (Ibuprofen) or Naprosyn (Naproxen) and the participant is unable to stop taking them 3 days before the biopsy and 1 day after the biopsy procedure. - Taking more than 81 mg of aspirin a day and the participant is unable to stop taking it for 3 days before the biopsy and 1 day after the biopsy procedure. - Allergic to Lidocaine (Xylocaine) or any other local anesthetic or the participant has had in the past a severe allergic reaction to similar drugs. - Allergic to topical betadine solution. - Severe allergy to adhesives found in tape. - HIV virus infection. - Hepatitis B or C or exposure within 6 months of visit. - History of diabetes (requiring any medical treatment other than diet and exercise) or fasting plasma glucose is greater than or equal to 126 mg/dL or HbA1c greater than or equal to 6.5%. - Clinically significant hormonal dysfunction (self-reported or laboratory values out of range. Mild hypothyroidism (TSH < 10 microIU/mL) in participants over 60 is not considered exclusion). - Kidney disease (Creatinine >1.5 mg/dl or calculated creatinine clearance < 50 cc/min) - Liver disease (Bilirubin > 1.5 mg/dl (unless higher levels can be ascribed to Gilbert s disease); ALT, AST or alkaline phosphatase twice the normal serum concentration) - Severe gastrointestinal diseases such as Crohn s disease or ulcerative colitis requiring continuous treatment. - History of severe pulmonary disease such as chronic obstructive pulmonary disease (COPD) or asthma requiring continuous medication use. - History of severe psychiatric conditions associated with behavioral problems or requiring chronic medical treatment. - Currently pregnant or breastfeeding. - Participants with history of skin keloid formation during wound healing - Current illness that as judged by the study physician substantially increases the risks associated the skin biopsy(s) (active infections, allergies, etc.).