A micrograph showing dispersed E. Coli bacteria (bright spots) expressing eGFP protein in highly monodisperse microdroplets. Both density, composition and size of the microdroplets can be finely controlled using droplet-based microfluidics. The digital microfluidic approach used here will allow us to monitor the change in cell growth and gene expression in individual bacteria and their progeny following a perturbation in their environment, such as the addition of antibiotics or the irradiation with UV light.