A method of crystallization is disclosed, the method comprises the steps of providing a microfluidic system comprising at least three channels having at least one junction; providing within the at least three channels a continuously flowing water-immiscible carrier-fluid, a continuously flowing first aqueous fluid comprising a crystallization target, and a continuously flowing second aqueous fluid comprising a precipitant; forming at least one plug comprising the first and second aqueous fluids by partitioning the aqueous fluids with the flowing carrier-fluid at the junction of the at least three channels, flowing the at least one plug through an outlet port into a tubing, and stopping the flow of the at least one plug in the tubing, wherein the crystallization target forms a crystal in the tubing.