A method of producing microspheres of a substance comprising a polymer comprising the steps of: a. dissolving said substance in a solvent to form a first fluid containing said substance; b. dispersing said first fluid in at least one second fluid to form an emulsion of micro droplets of said first fluid in a second fluid, said micro droplets having an average droplet size and having a droplet size distribution around said average droplet size and below a maximum droplet size, wherein said micro-droplets are generated by injecting said first fluid in at least one micro-channel of a micro-channel device, said micro-channel device comprising a channel plate that comprises said at least one micro-channel, said micro-channel having a cross-sectional diameter of a specific size and having an outlet that delivers said droplets at an output surface of said channel plate, said channel plate comprising at least one secondary channel that extends between a first end below an inlet surface and opening within a micro-channel and a second end that opens to said output surface of said micro-channel plate, and by ejecting droplets that emerge at said outlet of said at least one micro-channel in said second fluid. c. allowing said micro droplets of said first fluid to lose said solvent in said second fluid and to form microspheres containing said substance in said second fluid, said microspheres having an average particle size and having a particle size distribution around said average particle size and below a maximum particle size; and d. subjecting said second fluid containing said microspheres to a micro filter having a relatively narrow pore size distribution around an average pore size, which average pore size is between said average particle size and said maximum particle size to form a filtrate comprising a majority of said microspheres that is substantially void of microspheres having a particle size exceeding a maximum allowable particle size. a. dissolving said substance in a solvent to form a first fluid containing said substance; b. dispersing said first fluid in at least one second fluid to form an emulsion of micro droplets of said first fluid in a second fluid, said micro droplets having an average droplet size and having a droplet size distribution around said average droplet size and below a maximum droplet size, wherein said micro-droplets are generated by injecting said first fluid in at least one micro-channel of a micro-channel device, said micro-channel device comprising a channel plate that comprises said at least one micro-channel, said micro-channel having a cross-sectional diameter of a specific size and having an outlet that delivers said droplets at an output surface of said channel plate, said channel plate comprising at least one secondary channel that extends between a first end below an inlet surface and opening within a micro-channel and a second end that opens to said output surface of said micro-channel plate, and by ejecting droplets that emerge at said outlet of said at least one micro-channel in said second fluid. c. allowing said micro droplets of said first fluid to lose said solvent in said second fluid and to form microspheres containing said substance in said second fluid, said microspheres having an average particle size and having a particle size distribution around said average particle size and below a maximum particle size; and d. subjecting said second fluid containing said microspheres to a micro filter having a relatively narrow pore size distribution around an average pore size, which average pore size is between said average particle size and said maximum particle size to form a filtrate comprising a majority of said microspheres that is substantially void of microspheres having a particle size exceeding a maximum allowable particle size.