Stellar evolution models are a cornerstone of young star astrophysics, which necessitates that they yield accurate and reliable predictions of stellar properties. Here, I review the current performance of stellar evolution models against young astrop
hysical benchmarks and highlight recent progress incorporating non-standard physics, such as magnetic field and starspots, to explain observed deficiencies. While addition of these physical processes leads to improved agreement between models and observations, there are several fundamental limitations in our understanding about how these physical processes operate. These limitations inhibit our ability to form a coherent picture of the essential physics needed to accurately compute young stellar models, but provide rich avenues for further exploration.
Stellar fundamental properties (masses, radii, effective temperatures) can be extracted from observations of eclipsing binary systems with remarkable precision, often better than 2%. Such precise measurements afford us the opportunity to confront the
validity of basic predictions of stellar evolution theory, such as the mass-radius relationship. A brief historical overview of confrontations between stellar models and data from eclipsing binaries is given, highlighting key results and physical insight that have led directly to our present understanding. The current paradigm that standard stellar evolution theory is insufficient to describe the most basic relation, that of a stars mass to its radius, along the main sequence is then described. Departures of theoretical expectations from empirical data, however, provide a rich opportunity to explore various physical solutions, improving our understanding of important stellar astrophysical processes.
