Before revision: We present the first systematic measurement of critical dynamics of a 2D liquid with conserved order parameter embedded in bulk 3D fluid, here a lipid membrane in water .
After revision: Near a critical point, the time scale of thermally-induced fluctuations diverges in a manner determined by the dynamic universality class. Experiments have verified predicted 3D dynamic critical exponents in many systems, but similar experiments in 2D liquid with conserved order parameter embedded in bulk 3D fluid, here a lipid membrane in water .