Dripping and Jetting. When turning on the faucet, you might not pay too much attention to the flow rates that you are using. However, if the faucet was leaking last night, it might have kept you awake with its distressing sound of a constant drip. In hydrodynamics, these two different regimes are cleverly called the dripping and jetting regimes. Not surprising, these two regimes also exist in the breakup of drops in microfluidic devices. Microfluidics is the study and control of fluids at the length scale of the drops that are generated. Generating double emulsions, drops inside of drops, entails pushing three immiscible phases through a device. Here, we show water drops, dyed red and blue, inside of oil drops. The third aqueous phase, called the outer phase, is a carrier fluid that shears the oil drops, controls their size, and pushes the drops through the device. Depending on its flow velocity, the drops will either drip or jet. At high flow velocities of the outer fluid, and thus, high shear rates, but smaller flow rates of the inner fluids, “the dripping regime”, smaller drops are generated. This is shown in the top images and the bottom image on the left. Conversely at low flow velocities of the outer fluid, thus, low shear rates, but high flow rates of the inner fluids, “the jetting regime”, larger drops are generated. Large quantities of inner drops are encapsulated in the jetting regime because the inner flow rates are higher. While the overall drops are larger in this regime, there is also less control over the monodispersity of the outer drops. (Photo credits: L. L. A. Adams)