  We imaged the position of the Naked-Eye Burst, GRB080319B, before, during and
after its gamma-ray activity with sub-second temporal resolution and discovered
the fast variability of its prompt optical emission. Its characteristics and
similarity with properties of gamma emission temporal structure suggest that it
reflects the behaviour of internal engine -- supposedly, a hyperaccreting
solar-mass black hole formed in the collapse of a massive stellar core.
