  Apparently, Gamma-Ray Bursts (GRBs) are all but standard candles. Their
emission is collimated into a cone and the received flux depends on the cone
aperture angle. Fortunately we can derive the aperture angle through an
achromatic steepening of the lightcurve of the afterglow, and thus we can
measure the "true" energetics of the prompt emission. Ghirlanda et al. (2004)
found that this collimation-corrected energy correlates tightly with
thefrequency at which most of the radiation of the prompt is emitted. Through
this correlation we can infer the burst energy accurately enough for a
cosmological use. Using the best known 15 GRBs we find very encouraging results
that emphasize the cosmological GRB role. Probing the universe with high
accuracy up to high redshifts, GRBs establish a new insight on the cosmic
expanding acceleration history and accomplish the role of "missing link"
between the Cosmic Microwave Background and type Ia supernovae, motivating the
most optimistic hopes for what can be obtained from the bursts detected by
SWIFT.
