  We study concentrated colloidal suspensions, a model system which has a glass
transition. The non-equilibrium nature of the glassy state is most clearly
highlighted by aging -- the dependence of the system's properties on the time
elapsed since vitrification. Fast laser scanning confocal microscopy allows us
to image a colloidal glass and track the particles in three dimensions. We
analyze the static structure in terms of tetrahedral packing. We find that
while the aging of the suspension clearly affects its dynamics, none of the
geometrical quantities associated with tetrahedra change with age.
