The heart of our GCxGC system is the Loop Modulator: two short (3mm) column segments positioned at the intersection of two gas jets, one hot, one cold. The hot jet pulses every few seconds, causing effluent from a first capillary column to be cryo-cut, focused, and transmitted to a short, fast second column. Result: ~600 secondary chromatograms, together compromising a GCxGC image.