  Preons are hypothetic constituents of the standard particles. They were
initially assumed to have basically similar properties to those of conventional
matter. But this is not necessarily the case: the ultimate constituents of
matter may feel a different space-time from that of special relativity and
exhibit mechanical properties different from those predicted by standard
quantum mechanics. They can also play an important cosmological role
(inflation, dark matter, dark energy...). It is even not obvious that energy
and momentum would have to be conserved in such a scenario. In this series of
papers, we review the subject using the superbradyon model as an example, and
suggest new ways to explore possible tests of the preon hypothesis.
