This study is a prospective, single-center, blinded, non-randomized clinical trial. Two subjects who have chosen to have a surgical facelift procedure and agree to drink heavy water for tissue labeling, will be enrolled. Subjects will consume heavy water and collect saliva specimens over the course of the study period, following a specific heavy water labeling protocol. Two weeks after starting the heavy water protocol, subjects will return to the study site to receive one Ultherapy® treatment to the pre-auricular region on one side of the face. The contra-lateral pre-auricular region will serve as a control. Following Ultherapy® treatment, subjects will continue to follow the heavy water protocol for 4 more weeks. Subjects will then return to the study site to undergo resection of the treated and control tissue for analysis during their planned rhytidectomy procedure. Subjects will send in saliva samples on a weekly basis to allow for confirmation that they are drinking the heavy water.