This activity introduces droplet-based millifluidics and the usage of aqueous droplets as independent chemical microreactors for reaction-kinetics studies. Students build their own droplet generators from common macroscopic glassware and connecting parts to create trains of millimeter-sized droplets in which a redox reaction takes place. The activity allows students to work on reaction kinetics, hydrodynamics at low Reynolds numbers, and image analysis at the macroscopic scale.