Method of performing PCR reaction in continuously flowing microfluidic plugs

A method comprising the steps of:

• providing a microfluidic system comprising one or more channels;
• providing within the one or more channels a continuously flowing carrier fluid comprising an oil and a continuously flowing aqueous fluid comprising target DNA or RNA molecules and at least one other molecule in the fluid that can react with the target DNA or RNA molecules under conditions in which the target DNA or RNA molecules and the other molecules in the fluid do not react with each other;
• controlling flow rates of said aqueous fluid and said carrier fluid to partition the continuously flowing aqueous fluid with the continuously flowing carrier fluid to form a plurality of plugs of the aqueous fluid, each having a substantially uniform size of about 200 μm or less, wherein the target DNA or RNA in said plurality of plugs represents a Poisson distribution, and at least one member of said plurality comprises a single target DNA or RNA molecule and at least one of the other molecules that can react with the target DNA or RNA molecule;
• and
• providing conditions suitable for a polymerase-chain reaction in at least one plug of the plurality of plugs such that the target DNA or RNA is amplified.