A flow cell for a microfluidic device can include a chamber, first microfluidic entry and exit channels, second microfluidic entry and exit channels, a first electrode, and a second electrode. A microfluidic device can include a microfluidic channel, a laser to excite fluorescent material, and a detector to detect fluorescence emission. Methods of merging a droplet from an emulsion in to a second stream of fluid and of detecting a content of a droplet in a stream are further disclosed.