We offer a novel liquefier that has the potential to simultaneously increase thermodynamic efficiency and significantly reduce complexity. The ?active gas regenerative liquefier? (AGRL) uses an array of discrete micro compressor-expander units in a periodic heat exchanger to accomplish extremely efficient liquefaction of hydrogen and other cryogenic fluids. When an array of these units are combined into a highly effective regenerator with excellent heat transfer, low pressure drop, and low longitudinal conduction, the potential for a extremely efficient regenerative refrigerator and/or liquefier is created. The capability to directly couple the compression of a working gas within a unit with the simultaneous expansion of a working gas within the same unit allows distributed work input and recovery from near ambient temperature to cryogenic temperatures as low as ~20 K. By using this micro compressor-expander unit, the net work input is reduced substantially to that required for a very efficient refrigeration cycle, no matter what the temperature span of the liquefier.