Microfluidic devices capable of metering fluid flow are provided. Devices and methods for trunk-branch metering of fluid plugs in which one or more branch channels of defined volume are metered from a bulk fluid are described. Also described are the metering of at least one discrete plug by selecting the supply conditions of a first and a second fluid to a microfluidic channel. The first fluid may be a liquid and the second fluid a gas. Reduced-area channel segments are provided to assist with metering one or more discrete fluid plugs. In another aspect, a microfluidic volume is metered by filling a microfluidic chamber with fluid, sealing an inlet channel, and then extracting the fluid.
