Incremental change is intrinsic to both the initial development and subsequent evolution of large complex software systems. Evolve is a graphical design tool that captures this incremental change in the definition of software architecture. It supports a principled and manageable way of dealing with unplanned change and extension. In addition, Evolve supports decentralized evolution in which software is extended and evolved by multiple independent developers. Evolve supports a model-driven approach in that architecture definition is used to directly construct both initial implementations and extensions to these implementations. The tool implements Backbone - an architectural description language (ADL), which has both a textual and a UML2, based graphical representation. The demonstration focuses on the graphical representation.