  It has been recently proposed that current burst and afterglow observations
can be accounted for by a top hat jet structure as well as by a more universal
structured outflow, in which the energy carried by the flow is maximum at the
jet spine, decreasing outwards as a power-law with the off-axis angle. To pin
down the GRBs jet structure is important in order to quantify the total energy
released by the unknown engine and put constrains on its nature. In paper we
will review the most popular GRBs jet structures, focusing on the predicted
observed properties that could discriminate between them. In particular the
behaviour of linearly polarised emission during the afterglow phase seems very
promising, since the degree and temporal dependence are predicted to be very
different from model to model. In addition, polarization measurements and
detections are accumulating fast enouqgh to lead soon to a comprehension of
magnetic field and GRBs jet configurations.
