  Light scalar mesons are found to fit rather well a diquark-antidiquark
description. The resulting nonet obeys mass formulae which respect, to a good
extent, the OZI rule. OZI allowed strong decays are reasonably reproduced by a
single amplitude describing the switch of a qbar-q pair, which transforms the
state into two colourless pseudoscalar mesons. Predicted heavy states with one
or more quarks replaced by charm or beauty are briefly described; they should
give rise to narrow states with exotic quantum numbers.
