Higher-order precision calculations are typically associated with the
energy frontier in general and the LHC in particular. In this talk I
will discuss the 'why' and 'how' for computing QED corrections to
low-energy scattering and decay processes. The 'why' will be answered
by presenting a number of cases where QED corrections are crucial to
answer fundamental questions of particle physics. The 'how' will
address challenges that are particular to QED and often related to the
inclusion of mass effects.