Applications are emerging that require the creation of fine-scale structures in three dimensions — examples include scaffolds for tissue engineering1, micro-fluidic devices2 and photonic materials that control light propagation over a range of frequencies3. But writing methods such as dip-pen nanolithography4 and ink-jet printing5 are either confined to two dimensions or beset by wetting and spreading problems. Here we use concentrated polyelectrolyte inks to write three-dimensional microperiodic structures directly without using masks. Our technique enables us to write arbitrary three-dimensional patterns whose features are nearly two orders of magnitude smaller than those attained with other multilayer printing techniques6.