Inclusion Criteria:  Healthy men and women Women must be premenopausal with a regular menstrual cycle (26-30 days)  Exclusion Criteria:  History of autonomic dysfunction Cardiovascular diseases Diabetes Tobacco/nicotine use Systolic Pressure >= 130 mmHg Diastolic Pressure >= 85 mmHg Regular melatonin use >= 1 use/week Allergy to melatonin Cardiometabolic medication use (e.g. anti-hypertensives, insulin-sensitizing, statins) Sex hormone replacement medical use (e.g. testosterone, estrogen, progesterone) Pregnancy