Significant discrepancies between stellar evolution models and solar-type eclipsing and visual binaries ?

Individual components of well-detached binary systems are assumed to be two single-like stars with a common origin, i.e. they share the same chemical composition and same age. Therefore, one expects to fit the observed parameters of both components with a single isochrone at the same metallicity. We show that serious problems appear for systems with accurate fundamental data (eclipsing binaries in the field and in the Hyades, and a visual binary) in the 0.7-1.1 Msun mass range. We discuss and briefly review the results obtained so far on these objects. Finally, in an attempt to solve this problem, we present new projects, both on the theoretical and the observational sides.