A method for generating picodroplets from a suspension comprising a plurality of entities, the method comprising: providing a suspension by aligning entities in a suspension in a microfluidic structure, wherein aligning entities in a suspension in a microfluidic structure comprises: providing a main channel on said microfluidic structure for guiding said entities in said suspension; providing a first comb of first inlets arranged on a first side of said channel for introducing a fluid into said channel; providing a second comb of second inlets arranged on a second side of said channel for introducing a said fluid into said channel; wherein said first side is opposite said second side, and wherein a said first inlet has a corresponding, respective one of said second inlets at a substantially similar longitudinal position along said main channel, and wherein the first comb of inlets and the second comb of inlets have identical length and cross-section; providing a first plurality of spacing fluid channels and a second plurality of spacing fluid channels for providing the said fluid into the first comb of first inlets and the second comb of second inlets, wherein the first plurality of spacing fluid channels and the second plurality of spacing fluid channels comprise one main spacing fluid channel which joins a plurality of secondary spacing fluid channels, wherein the secondary spacing fluid channels join the first comb of first inlets and the second comb of second inlets; and wherein said first comb of first inlets and said second comb of second inlets comprise a plurality of pairs of inlets joined at an acute angle to the main channel, wherein the secondary spacing fluid channels are smaller than the main spacing fluid channels, and wherein each of said plurality of first inlets and second inlets is smaller than the plurality of spacing fluid channels and the main channel; and the method further comprising: guiding said suspension comprising said entities through said channel; and introducing said fluid into said channel from one or more of said first inlets at the same time as introducing said fluid into said channel from one or more corresponding, respective said second inlets to align said entities in said suspension in said channel, wherein fluid is introduced from the one or more of said first inlets and the one or more corresponding, respective said second inlets with identical flow rates; and forming an emulsion of picodroplets comprising said entities by providing a flow of said suspension to a picodroplet generation region of said microfluidic structure. providing a main channel on said microfluidic structure for guiding said entities in said suspension; providing a first comb of first inlets arranged on a first side of said channel for introducing a fluid into said channel; providing a second comb of second inlets arranged on a second side of said channel for introducing a said fluid into said channel; wherein said first side is opposite said second side, and wherein a said first inlet has a corresponding, respective one of said second inlets at a substantially similar longitudinal position along said main channel, and wherein the first comb of inlets and the second comb of inlets have identical length and cross-section; providing a first plurality of spacing fluid channels and a second plurality of spacing fluid channels for providing the said fluid into the first comb of first inlets and the second comb of second inlets, wherein the first plurality of spacing fluid channels and the second plurality of spacing fluid channels comprise one main spacing fluid channel which joins a plurality of secondary spacing fluid channels, wherein the secondary spacing fluid channels join the first comb of first inlets and the second comb of second inlets; and wherein said first comb of first inlets and said second comb of second inlets comprise a plurality of pairs of inlets joined at an acute angle to the main channel, wherein the secondary spacing fluid channels are smaller than the main spacing fluid channels, and wherein each of said plurality of first inlets and second inlets is smaller than the plurality of spacing fluid channels and the main channel; and the method further comprising: guiding said suspension comprising said entities through said channel; and introducing said fluid into said channel from one or more of said first inlets at the same time as introducing said fluid into said channel from one or more corresponding, respective said second inlets to align said entities in said suspension in said channel, wherein fluid is introduced from the one or more of said first inlets and the one or more corresponding, respective said second inlets with identical flow rates; and forming an emulsion of picodroplets comprising said entities by providing a flow of said suspension to a picodroplet generation region of said microfluidic structure. guiding said suspension comprising said entities through said channel; and introducing said fluid into said channel from one or more of said first inlets at the same time as introducing said fluid into said channel from one or more corresponding, respective said second inlets to align said entities in said suspension in said channel, wherein fluid is introduced from the one or more of said first inlets and the one or more corresponding, respective said second inlets with identical flow rates; and forming an emulsion of picodroplets comprising said entities by providing a flow of said suspension to a picodroplet generation region of said microfluidic structure.