HIFU stands for High-Intensity Focused Ultrasound. It is a non-surgical treatment that uses focused ultrasound energy to deliver controlled heat to specific depths beneath the skin, typically the upper and mid-dermis and the deeper SMAS layer that a surgeon would tighten during a facelift. The heat is intended to stimulate the body's natural repair response, encouraging fresh collagen to form over the following weeks so the skin gradually looks firmer and a little lifted.