Examples include microfluidic devices. Example microfluidic devices include a first microfluidic channel, a second microfluidic channel, and a third microfluidic channel fluidly coupled to the first microfluidic channel and the second microfluidic channel via a fluid junction. A fluid actuator is disposed in the third microfluidic channel to actuate to thereby pump a first fluid and a second fluid into the third microfluidic channel.