Performing radiolabeling in microvolume reactors (1–10 μL) instead of conventional reactors (~1 mL) offers significant improvements including increased yield, high molar activity, short synthesis time, reduced reagent consumption, and reduced amount of byproducts that need to be removed during purification. Furthermore, microreactor-based radiochemistry systems are emerging that are far more compact than conventional radiosynthesizers, providing the potential for lower cost radiochemistry facilities and adoption of a wider distributed manufacturing paradigm that can support flexible and scalable manufacturing of a wide variety of radiopharmaceuticals at a given radiopharmacy site. In this chapter, we focus on droplet-based reactors as a way to realize these benefits and review recent work on implementing droplet-based reactions, highlighting technical progress, radiosynthesis applications, and advantages and limitations of each droplet platform.