When the Tomcat servlet engine was first developed, its only purpose in life was as the reference implementation for the Java Servlet Specification. As often happens when time pressures intervene, there was no time to consider the overall architecture in a meaningful way. Now that Tomcat is an open source project, we have the opportunity to define an architecture that makes Tomcat easy to understand, easy to extend, and easy to embed. We'll look at the proposed architecture for Tomcat 2.0--a component-based design with plug-in replacement of existing functional components, as well as custom extensions to the request processing performed by the basic engine. These new capabilities will make it easy to embed Tomcat as a servlet container in environments ranging from a hardware device to the most sophisticated application server environments.