Just a drop. In the field of biological research and biotechnology, fast and efficient screening for particular properties of minute quantities down to single-particle level has become increasingly important. This work describes the implementation of a lab-on-chip device to generate small reaction containers, that is, a homodisperse water-in-oil emulsion, and cell-free expression of the green fluorescent protein inside the aqueous droplets. Detection of the autofluorescent protein was performed by confocal fluorescence spectroscopy.