How small can a laser be made? What characteristic properties must a device possess to still be called a laser? How can one prove laser action in the limiting cases of single-emitter and thresholdless operation? What are the prospects and the application potential of semiconductor nanolasers, and where does the ongoing miniaturization lead to? This topical review focuses on the role that quantum-dot micro-and nanolasers have played in these developments and on the impressive progress that has been made over the last decade in this field, with an emphasis on quantum dot-micropillar lasers. We discuss the design, modeling, fabrication, and quantumoptical characterization of quantum-dot micropillar lasers, attempt to provide answers to the above questions, and give an outlook on the direction of development of the field and on exciting opportunities for future applications of micro-and nanoscale lasers in quantum nanophotonics.