A quantum point contact which is nearly pinched off (so that its conductance is less than 2e2/h) is a tunnel barrier of adjustable height for electrons near the Fermi level. This property has been used to inject and detect electrons in a small confined region of a 2D electron gas, called a quantum dot. A quantum dot coupled to the outside by a pair of quantum point contacts has provided an ideal model system for the investigation of the effects of Coulomb repulsion on resonant tunneling. (See PHYSICS TODAY, January 1993, page 24.)The zero-dimensional quantum dot forms the logical end to the reduction of dimensionality of the two-dimensional electron gas. In this article we have reviewed the role played by the one-dimensional quantum point contact in the conceptual development started by Landauer four decades ago. The concept of electrical conductance was conceived in the nineteenth century, at a time when the electron was not even discovered. It is amusing that it required the sophisticated micro-electronics technology of the late twentieth century to demonstrate experimentally that "conduction is transmission".