The present application provides methods and devices for producing micro-fluids. Each device comprises a plurality of parallel inlet channels, an intersection and a plurality of parallel outlet channels. The plurality of parallel inlet channels comprises a first set of inlet channels for introducing a first fluid at a first flow rate, a second set of inlet channels for introducing a second fluid at a second flow rate and a third set of inlet channels for introducing a third fluid at a third flow rate. Once introduced, the first fluid, the second fluid and the third fluid flow through the corresponding channels to intersect at the intersection and form micro-fluids, which can be collected from the plurality of parallel outlet channels.