Defining the regions (1 – 1000) μl/min as microflow and (1 – 1000) nl/min as nanoflow, this white paper describes various principles for a primary realization of the measurement. In this document we briefly describe some common principles for flow rate calibrations. Typically, the gravimetric approach is used for microflow rates. For nanoflow rates potential methods are based on volumetric expansion and optic measurement of the dispensed volume.