A material transport and event control in systems with piezoelectrically activated droplet emission including a device for metering a material into a carrier matrix, having a carrier matrix source (0) supplying a carrier matrix, a supply vessel (1) filled with the material in preferably liquid form, a metering unit (3, 4) including a metering chamber (4), disposed downstream of the carrier matrix source and a metering head (3 disposed downstream of the supply vessel and configured preferably for piezoelectrically activated droplet emission, the carrier matrix being supplied to the metering chamber from the carrier matrix source, and the material being supplied to the metering head from the supply vessel, being emitted via the metering head into the metering chamber and consequently being metered into the carrier matrix, including a pressure control device configured to control the pressure in the supply vessel (1) and/or the pressure in the metering unit.