  We present an extraordinary variation of the X-ray spectrum of the obscured
AGN in NGC 1365, which was observed by Chandra to change from Compton-thin to
Compton-thick and back to Compton-thin in four days. This fast variation imply
a a size of ~10^14 cm for the emitting region, and an extremely compact size
(~10^16 cm) of the clumpy circumnuclear absorber.
