The densification of regional seismic networks, the proliferation of temporary portable seismometer deployments, and the increasing ease with which traditional seismic array data may be obtained, all facilitate a new wave of imaging Earth's interior at the shortest-ever possible scale lengths using array methods. In fact, seismic array techniques are often necessary for retrieval of subtle, yet important, deep Earth seismic structures, particularly those containing fine-scale features. While only a handful of investigations over the past few decades have used traditional seismic array processing for imaging Earth's deep interior, the recent data renaissance in our community enables utilization of methods once predominantly devoted to the near surface for peering deep into the planet, from upper mantle discontinuities to the solid inner core, from the earthquake source to near-surface receiver structure.