The sheer complexity of today's embedded systems forces designers to start with modeling and simulating system components and their interactions in the very early design stages. It is therefore imperative to have good tools for exploring a wide range of design choices, especially during the early design stages, where the design space is at its largest. This paper presents an overview of the Sesame framework, which provides high-level modeling and simulation methods and tools for system-level performance evaluation and exploration of heterogeneous embedded systems. More specifically, we describe Sesame's modeling methodology and trajectory. It takes a designer systematically along the path from selecting candidate architectures, using analytical modeling and multiobjective optimization, to simulating these candidate architectures with our system-level simulation environment. This simulation environment subsequently allows for architectural exploration at different levels of abstraction while maintaining high-level and architecture-independent application specifications. We illustrate all these aspects using a case study in which we traverse Sesame's exploration trajectory for a motion-JPEG encoder application.