Jullie Nollsch, United Blood Services assistant donor care supervisor, inserts a needle into the arm of Senior Airman Haylley Carlson, 28th Medical Group physical therapy assistant, during a blood drive at Ellsworth Air Force Base, S.D., April 2, 2012. UBS conducts several blood drives throughout the year at a variety of locations. Blood can be stored for only 42 days, so a continual fresh supply is crucial. (U.S. Air Force photo by Airman 1st Class Kate Thornton/Released)