A catenoid is a surface in 3-dimensional Euclidean space arising by rotating a catenary curve about its directrix. Not counting the plane, it is the first minimal surface to be discovered. It was found and proved to be minimal by Leonhard Euler in 1744. Early work on the subject was published also by Jean Baptiste Meusnier. There are only two minimal surfaces of revolution (surfaces of revolution which are also minimal surfaces): the plane and the catenoid.The catenoid may be defined by the following parametric equations:In cylindrical coordinates:A physical model of a catenoid can be formed by dipping two circles into a soap solution and slowly drawing the circles apart.The catenoid may be also defined approximately by the Stretched grid method as a facet 3D model