In the early hours of July 28 2006 (MJD 53944) the High Energy Stereoscopic System (H.E.S.S.) observed an unprecedented VHE (>100 GeV) flux state of the BL Lac object PKS 2155-304 (z=0.116). The average flux of the source exceeded that of the Crab nebulae (>200 GeV) by a factor of 7. This is by far the highest flux state ever detected from PKS 2155-304 and it is one of the highest among all the BL Lac objects. The high sensitivity of H.E.S.S. (5\sigma detection in ~30 s for a Crab nebulae flux source at 20 degrees zenith angle) enables for the first time VHE-flux variability studies on time scales of tens of seconds. The issues that are going to be discussed are the cross correlation and the cross spectrum analysis between the VHE bands together with some constraints concerning the black hole mass and the Doppler factor.