  I list the characteristic features of Globular Cluster (GC) HR diagrams which
provide a complete test of the stellar evolution of low mass stars:
morphologies describing the different evolutionary phases, number ratios and
luminosity functions, which add quantitative information. Then I explore the
stage of todays' understanding of the classical distance scale indicators
(providing warnings against model construction which, underneath, already is
based on a choice of distance), and compare them to the `new' indicators, such
as the white dwarfs and the first and second kink of the low main sequence. The
classical and new distance indicators are still subject to uncertainties due to
tiny details of the theory, which are all of the same order of magnitude,
\~0.25mag and the absolute ages of GCs can not be constrained to better than
10-16Gyr. However, most of recent theoretical and observational results
(including both classical and new indicators) point more towards the lower
range of ages (10-12) than to the upper range (15-16).
