Sensitised luminescence from lanthanide complexes offers many potential advantages in imaging and assay, particularly when coupled with time-gating protocols that can be used to gate out background signal. In this perspective, we discuss the routes by which lanthanide arrays and polymetallic d–f hybrids can be prepared by conventional synthesis and self-assembly, and discuss and evaluate the possibilities for exploiting and evaluating the intermediates in the sensitisation process, with particular emphasis on the mechanisms of energy transfer.