The droplet and species dynamics are studied using high-speed videomicroscopy and fluorescence microscopy. The focus is on the role of the liquid pores as transient sieves. One important goal is to identify and understand the main mechanisms of passage of the dissolved/suspended species through the liquid pores. The influence of the main control parameters (for example the voltage and the viscosity of the oil phase) is examined, with the aim to identify especially favorable regions in the parameter space for species separation.