  We present multiple Chandra and XMM-Newton observations of the type 1.8
Seyfert Galaxy NGC 1365, which shows the most dramatic X-ray spectral changes
observed so far in an AGN: the source switched from reflection dominated to
transmission dominated and back in just 6 weeks. During this time the soft
thermal component, arising from a ~1 kpc region around the center, remained
constant. The reflection component is constant at all timescales, and its high
flux relative to the primary component implies the presence of thick gas
covering a large fraction of the solid angle. The presence of this gas, and the
fast variability time scale, suggest that the Compton-thick to Compton thin
change is due to variation in the line-of-sight absorber, rather than to
extreme intrinsic emission variability. We discuss a structure of the
circumnuclear absorber/reflector which can explain the observed X-ray spectral
and temporal properties.
