All-aqueous emulsions are conventionally formed at bulk scale by mild shaking of aqueous two-phase systems. They can be used to carry out reactions both in droplets (compartmentalized) and on droplet surfaces in conditions free of synthetic surfactants and organic solvents. The use of all-aqueous emulsions for extractive bioconversion is a routine application; however, these emulsions hold many more promises. A renowned, rapidly evolving application is bio-microgel synthesis through biopolymer crosslinking within the emulsion internal phase. When polyelectrolyte crosslinking is achieved at the interface rather than in droplets, microcapsules can be formed, and when in situ colloidal particle generation at the droplet surface is obtained, colloidosomes are produced. The use of microfluidics to control the formation of all-aqueous emulsions offers many advantages in reactions monitoring and partitioning of reactants.