Anhydrous microparticles, including a wide variety of organic and inorganic microspheres (e.g., silicone elastomers, metal oxides, metal organic frameworks), are attracting substantial attention for applications ranging from drug delivery to photocatalysis. Microfluidic materials synthesis techniques are an ideal approach for controlled synthesis of anhydrous microparticles. In this article, we highlight the recent developments using plug-and-play microfluidic reactors for anhydrous microparticle synthesis. We discuss assembly of capillary-based microfluidic reactors, their advantages compared to microfabricated chips, and basics of their operation. Furthermore, various types of anhydrous organic and inorganic microparticles synthesized in flow utilizing such microfluidic reactors are discussed in detail. Finally, we present new directions for microparticle synthesis using plug-and-play microfluidic reactors.