Droplet microfluidics enables experimentation and analysis of sample volumes on the order of femtolitres (10⁻¹⁵ litres),¹  while the samples remain physically separated. The droplets can also be generated at a high rate and with monodispersity.²  Each droplet can accordingly be used as a microreactor for individual experiments, providing high precision and accuracy. Various techniques and methods have been developed to manipulate the droplets to make the system more versatile. The common manipulation tasks are generating,³  trapping,⁴  sorting,⁵  coalescence,⁶  mixing⁷  and lastly splitting⁸  of droplets using both passive and active methods. Passive methods involve permanent structures or adjustment of operation and device parameters. Passive methods do not provide selectivity, are rigid and affect all generated droplets. Active methods introduce external energy into the microfluidic system and induce additional force for the manipulation tasks mentioned above. The actuation mechanism can be precisely controlled to target specific droplets, taking advantage of its fast response time.^9–11  As such, this chapter focuses on active controls in droplet manipulation.