This article presents a general introduction to the thermophysical and dynamical properties of supercritical fluids. It is organized in two parts: in a first section, the nature of the critical point is discussed and its influence on the properties of supercritical fluids is presented; in a second section, we then examine the dynamic processes induced by these peculiar properties, concentrating on heat and mass transfer and more generally on relaxation phenomena. (C) 2010 Elsevier B.V. All rights reserved.