  We report on the discovery of periodic coronal rain in an off-limb sequence
of {\it Solar Dynamics Observatory}/Atmospheric Imaging Assembly images. The
showers are co-spatial and in phase with periodic (6.6~hr) intensity pulsations
of coronal loops of the sort described by Auchere et al. (2014) and Froment et
al. (2015, 2017). These new observations make possible a unified description of
both phenomena. Coronal rain and periodic intensity pulsations of loops are two
manifestations of the same physical process: evaporation / condensation cycles
resulting from a state of thermal nonequilibrium (TNE). The fluctuations around
coronal temperatures produce the intensity pulsations of loops, and rain falls
along their legs if thermal runaway cools the periodic condensations down and
below transition-region (TR) temperatures. This scenario is in line with the
predictions of numerical models of quasi-steadily and footpoint heated loops.
The presence of coronal rain -- albeit non-periodic -- in several other
structures within the studied field of view implies that this type of heating
is at play on a large scale.
