Impacts from space leave dramatic craters on planetary surfaces. Alterations also occur at the microscopic scale in the rocks of the crater itself due to the extreme shock pressures and elevated temperatures associated with these high-speed impact events. This chapter discusses these metamorphic impact features and explains how they arise. The chapter begins with some of the theoretical background to shock physics and why high-speed impacts (which lead to shocks) are commonplace in the Solar System. It then describes laboratory methods of reproducing shock events before describing the consequences of shocks on rock samples and how these can be used to subsequently gauge the peak shock pressure to which a sample was subjected.