Abstract: A flow cell is provided for the analysis and/or microscopy of liquid or gas samples on the nanometer to micron scale. The flow cell preferably includes a thin membrane that is transparent to electrons and/or photons, thereby enabling the penetration of electrons or photons into a liquid flowing through the cell. Trenches are provided on either side of the membrane, which advantageously minimize fluidic resistance outside of the window area of the cell and also enable a faster response time in response to changes in external fluidic pressure. This feature enables active feedback using pathlength sensitive probes to stabilize the fluid flow to thin streams from nanometer to micron scale thicknesses with nanometer precision.