  Detached eclipsing double line spectroscopic binaries offer an opportunity to
measure directly stellar parameters: mass, luminosity, radius, as well as the
distance. The only non-trivial step is the need to determine surface brightness
of each component on the basis of something measurable, like the color or the
line ratios. Modern model atmospheres provide a fairly good calibration of that
relation, but empirical verification is possible, and it is needed to achieve
the highest accuracy. When this approach is fully developed the detached
eclipsing binaries should provide direct (single step) distances with about 1%
accuracy to all galaxies in the Local Group. Recent discovery of numerous
detached eclipsing binaries near the main sequence turn-off points in several
globular clusters (Kaluzny et al. 1996a,b) will be followed by accurate
determinations of distances, masses and luminosities. The empirical the mass -
luminosity relation near the main sequence turn-off point will allow accurate
age and helium determinations, and a check on the stellar evolution theory.
