*Models* are abstract representations of the real world. A well-defined model is associated with a target system or phenomenon of interest, and can be used for either explanatory and/or predictive purposes. *Modeling* is the iterative process through which models and systems are brought into better agreement, either by refining the model or the target system itself. As a practice integral to experimental physics, modeling often appears as a learning goal for undergraduate physics laboratory courses at both the national and local levels.

We have investigate students' use of modeling in lab courses in a variety of ways. We developed the Experimental Modeling Framework (EMF) to characterize students' model-based reasoning and to inform the development of instructional lab environments that engage students in the process of modeling. We have applied this framework in the context of upper-level lab courses. We have also developed an assessment (MAPLE) to evaluate students' model-based reasoning.

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