A method, comprising: providing a microfluidic device (58, 100) in a pressure chamber comprising a plurality of droplet-making units (51, 52, 53, 54, 55, 100, 191, 192, 193), each of the droplet-making units in fluidic communication with a different source of droplet fluid (21, 22, 23, 24, 25, 105) and a common source of carrier fluid, each of the droplet-making units comprising an outlet channel (138, 172, 173, 174, 175) exiting an intersection, each of the outlet channels in fluidic communication with a common collector channel (77, 171,); applying the same pressure and/or pressure drop via the pressure chamber to all of the different sources of droplet fluid to cause droplet fluid (31, 32, 33, 34, 35, 105) to move from the different sources of droplet fluid into the common collector channel; and producing, within the microfluidic device, a set comprising a plurality of droplets (71, 72, 73, 74, 75, 135), each droplet of the set comprising droplet fluid from only one of the different sources of droplet fluid, the plurality of droplets of the set being contained within carrier fluid (62, 115) from the common source of carrier fluid wherein at least one of the droplet-making units comprises: an inlet for receiving droplet fluid from one of the different sources of droplet fluid, the inlet in fluidic communication via a first microfluidic channel with the intersection of microfluidic channels; and a second microfluidic channel (66, 119, 111, 161) extending from the intersection, the second microfluidic channel in fluid communication with the common source of carrier fluid; wherein at least one of the first or second microfluidic channels has a length within the droplet-making unit that is greater than two times the largest dimension of the droplet-making unit, the largest dimension of the droplet-making unit being the longest straight line that can be completely contained within the droplet-making unit. providing a microfluidic device (58, 100) in a pressure chamber comprising a plurality of droplet-making units (51, 52, 53, 54, 55, 100, 191, 192, 193), each of the droplet-making units in fluidic communication with a different source of droplet fluid (21, 22, 23, 24, 25, 105) and a common source of carrier fluid, each of the droplet-making units comprising an outlet channel (138, 172, 173, 174, 175) exiting an intersection, each of the outlet channels in fluidic communication with a common collector channel (77, 171,); applying the same pressure and/or pressure drop via the pressure chamber to all of the different sources of droplet fluid to cause droplet fluid (31, 32, 33, 34, 35, 105) to move from the different sources of droplet fluid into the common collector channel; and producing, within the microfluidic device, a set comprising a plurality of droplets (71, 72, 73, 74, 75, 135), each droplet of the set comprising droplet fluid from only one of the different sources of droplet fluid, the plurality of droplets of the set being contained within carrier fluid (62, 115) from the common source of carrier fluid wherein at least one of the droplet-making units comprises: an inlet for receiving droplet fluid from one of the different sources of droplet fluid, the inlet in fluidic communication via a first microfluidic channel with the intersection of microfluidic channels; and a second microfluidic channel (66, 119, 111, 161) extending from the intersection, the second microfluidic channel in fluid communication with the common source of carrier fluid; wherein at least one of the first or second microfluidic channels has a length within the droplet-making unit that is greater than two times the largest dimension of the droplet-making unit, the largest dimension of the droplet-making unit being the longest straight line that can be completely contained within the droplet-making unit. an inlet for receiving droplet fluid from one of the different sources of droplet fluid, the inlet in fluidic communication via a first microfluidic channel with the intersection of microfluidic channels; and a second microfluidic channel (66, 119, 111, 161) extending from the intersection, the second microfluidic channel in fluid communication with the common source of carrier fluid; wherein at least one of the first or second microfluidic channels has a length within the droplet-making unit that is greater than two times the largest dimension of the droplet-making unit, the largest dimension of the droplet-making unit being the longest straight line that can be completely contained within the droplet-making unit.