Revisiting Empirical Rules. Large databases of experimentally determined crystal structures have been analysed to uncover trends in the packing preferences of organic molecules. The availability of high quality crystal energy landscapes should allow organic solid state researchers to gain deeper insight into these preferences and, we hope, to discover new rules that will benefit the field of crystal engineering. We give two examples here: the unequal frequency with which molecules occupy the possible space groups and the spontaneous resolution of chiral molecules.