  The properties of the groundstate and first excitations of 2dimensionnal
quantum antiferromagnets are rapidly sketched. A special emphasis is put on the
gapped phases: Valence Bond Crystals and the two types of Spin Liquids. New
results on the spin susceptibility of small samples of the Heisenberg
antiferromagnet on a kagom\'e lattice are displayed for comparison with
Kagemaya {\it et al.} experimental result (this conference).
