This paper reports on the fabrication and characterization of liquid and gaseous jets ejected from microfabricated nozzles with dimensions ranging from 500 nm to 12 μm. Unlike previous work reporting the fabrication of nano-orifices defined within the thickness of the substrates [1-4], the in-plane nanonozzles presented in this paper are designed to sustain the high pressures necessary to obtain substantial nanofluidic jet flows. This approach also allows important three-dimensional features of nozzle, channel and fluidic reservoir to be defined by design and not by fabrication constraints, thereby meeting important fluid-mechanical criteria such as a fully-developed flow. The shrinking jet dimensions demand new metrology tools to investigate their flow behavior. A laser shadowgraphy technique is used to visualize and image the jet flows. Micromachined heated and piezoresistive cantilevers are used to investigate the thrust and heat flux characteristics of the jets.