Sound wave enables the sensation of hearing, and is an important way of communicating in the animal world. In physics, sound is considered as a mechanical vibration that can propagate in gases, liquids and solids. A research team from the Singapore University of Technology and Design (SUTD), led by Assistant Professor Dr Ye Ai, is studying the interactions between ultrasound (beyond the audible limit of human hearing) and micron-sized objects (e.g. biological cells) suspended in aqueous solutions. Dr Ai’s research team recently developed a highly accurate single cell level sorting technology using a highly focused sound wave beam (50 μm wide roughly ¼ of a single human hair’s diameter). This new cell manipulation technology enables highly accurate isolation of rare cell populations in complex biological samples. More concisely, it provides the potential of finding a single cell in a million.