  The transient behaviour of highly concentrated colloidal liquids and
dynamically arrested states (glasses) under time-dependent shear is reviewed.
This includes both theoretical and experimental studies and comprises the
macroscopic rheological behaviour as well as changes in the structure and
dynamics on a microscopic individual-particle level. The microscopic and
macroscopic levels of the systems are linked by a comprehensive theoretical
framework which is exploited to quantitatively describe these systems while
they are subjected to an arbitrary flow history. Within this framework,
theoretical predictions are compared to experimental data, which were gathered
by rheology and confocal microscopy experiments, and display consistent
results. Particular emphasis is given to (i) switch-on of shear flow during
which the system can liquify, (ii) switch-off of shear flow which might still
leave residual stresses in the system, and (iii) large amplitude oscillatory
shearing. The competition between timescales and the dependence on flow history
leads to novel features in both the rheological response and the microscopic
structure and dynamics.
