Here we propose two different ways to generate either monodisperse microemulsions or monodisperse microbubbles. The first of these techniques, the coflow configuration, consists of a flow rate Q i of a fluid with a viscosity μ i that discharges into an immiscible liquid of viscosity μ o that flows in parallel with the axis of the injector. When operating under the appropriate conditions, concentrated emulsions composed of micronsized drops with a narrow size distribution can be generated. Nevertheless, this procedure is not equally valid to generate the type of monodisperse bubbles required in many different pharmaceutical, medical and material science applications. As a consequence, we propose a variant of the coflow configuration implemented in a two-dimensional PDMS device for the production of ∼ 5 μm bubbles with a polydispersity index below 5% at high production rates (> 10 5 bubbles/s).