Two dimensional (2D) semiconductors, such as MoSe2 and WSe2, host tightly bound excitons (electron-hole pairs) that interact strongly with light. These monolayer semiconductors can be stacked together to realize heterostructures that exhibit new excitonic effects. In this presentation, I will discuss the optical response of two different 2D semiconductor heterostructures. First, I will review the progress towards understanding interlayer excitons in MoSe2-WSe2 heterobilayers. These interlayer excitons host a rich moiré physics associated with the spatially modulated interactions between layers. I will discuss our recent discoveries related to the origin of spectrally narrow photoluminescence from single photon emitters in these heterostructures. Interlayer excitons also possess a large permanent dipole moment that allows for their energy to be tuned with an out-of-plane electric field. By nano-patterning a gate on top of the MoSe2-WSe2 heterostructure, we are able to realize quantum dot-like potentials, which have potential applications toward realizing deterministic single photon emitters. Using the same architecture, we have demonstrated high speed interlayer exciton currents based on “slide” like quasi-one dimensional channels which have applications to excitonic circuitry.