Thermo-responsive microcrystals exhibiting obvious emission intensity or color changes have great potentials in sensing, information encryption, and microelectronics. We report herein the binary assembly of a blue-emissive iridium complex and a red-emissive ruthenium complex into homogeneously-doped or optically-heterostructured microcrystals with thermo-responsive properties. Depending on the assembly conditions, lateral or longitudinal triblock heterostructures with a microplate shape are obtained, which display distinct emission pattern changes upon heating as a result of the decreased efficiency of energy transfer. In addition, branched heterostructures are prepared by a stepwise assembly. The luminescence polarization of the homogeneously-doped binary crystals and the waveguiding property of the longitudinal triblock heterostructure are further examined. This work evidences the versatility of transition metal complexes in the assembly into various luminescent nano/micro structures with potential applications in thermo-sensing and nanophotonics.