A nucleic acid amplification method comprising: flowing a miscible phase fluid solution of nucleic acids and amplification reagents in a channel of a microfluidic device; contacting the miscible phase fluid solution of nucleic acids and amplification reagents with an immiscible phase fluid, wherein the contacting of the miscible phase fluid solution of nucleic acids and amplification reagents with the immiscible phase fluid results in the formation of miscible phase microdroplets surrounded by the immiscible phase fluid; flowing the miscible phase microdroplets surrounded by the immiscible phase fluid in a channel of a microfluidic device; contacting the miscible phase microdroplets surrounded by the immiscible phase fluid with a miscible phase carrier fluid, wherein the contacting of the miscible phase microdroplets surrounded by the immiscible phase fluid with the miscible phase carrier fluid results in the formation of multiple-emulsion microdroplets comprising a miscible phase microdroplet surrounded by the immiscible phase fluid, wherein the immiscible phase fluid is surrounded by the miscible phase carrier fluid; subjecting the multiple-emulsion microdroplets to amplification conditions sufficient to result in amplification of a target nucleic acid when present in the miscible phase fluid solution of nucleic acids to thereby form an amplification product; detectably labelling the amplification product subsequent to amplification with a fluorescent label and sorting the multiple-emulsion microdroplets via fluorescence activating cell sorting through flow cytometry, wherein the detectably labelling comprises adding a detectable label to the miscible phase carrier fluid, wherein the detectable label diffuses from the miscible phase carrier fluid, through the immiscible phase fluid, and into the miscible phase fluid solution; and detecting an amplification product resulting from the amplification of the target nucleic acid when present in the miscible phase fluid solution of nucleic acids. flowing a miscible phase fluid solution of nucleic acids and amplification reagents in a channel of a microfluidic device; contacting the miscible phase fluid solution of nucleic acids and amplification reagents with an immiscible phase fluid, wherein the contacting of the miscible phase fluid solution of nucleic acids and amplification reagents with the immiscible phase fluid results in the formation of miscible phase microdroplets surrounded by the immiscible phase fluid; flowing the miscible phase microdroplets surrounded by the immiscible phase fluid in a channel of a microfluidic device; contacting the miscible phase microdroplets surrounded by the immiscible phase fluid with a miscible phase carrier fluid, wherein the contacting of the miscible phase microdroplets surrounded by the immiscible phase fluid with the miscible phase carrier fluid results in the formation of multiple-emulsion microdroplets comprising a miscible phase microdroplet surrounded by the immiscible phase fluid, wherein the immiscible phase fluid is surrounded by the miscible phase carrier fluid; subjecting the multiple-emulsion microdroplets to amplification conditions sufficient to result in amplification of a target nucleic acid when present in the miscible phase fluid solution of nucleic acids to thereby form an amplification product; detectably labelling the amplification product subsequent to amplification with a fluorescent label and sorting the multiple-emulsion microdroplets via fluorescence activating cell sorting through flow cytometry, wherein the detectably labelling comprises adding a detectable label to the miscible phase carrier fluid, wherein the detectable label diffuses from the miscible phase carrier fluid, through the immiscible phase fluid, and into the miscible phase fluid solution; and detecting an amplification product resulting from the amplification of the target nucleic acid when present in the miscible phase fluid solution of nucleic acids.