Quantum dot (QD) superlattices have the potential to provide new optical properties and functions based on interactions between adjacent QDs. Two types of interactions occur between the QDs: energy transfer (ET) from small-sized QDs to large QDs and resonant coupling between QDs with equal eigenenergies. Since ET and resonant coupling strongly depend on the distance between QDs, it is critical to precisely control the distance to understand the interaction mechanism. In this review, we describe that the distance between QDs can be controlled with an accuracy of 1 nm by a layer-by-layer method and further explain the mechanisms of ET and resonant coupling between adjacent QDs. (C) 2017 Elsevier B.V. All rights reserved.