  We present a slightly modified version of the well known "geometric Lorenz
attractor". It consists in a C1 open set O of vector fields in R3 having an
attracting region U containing: (1) a unique singular saddle point sigma; (2) a
unique attractor Lambda containing the singular point; (3) the maximal
invariant in U contains at most 2 chain recurrence classes, which are Lambda
and (at most) one hyperbolic horseshoe. The horseshoe and the singular
attractor have a collision along the union of 2 co-dimension 1 sub-manifolds
which divide O in 3 regions. By crossing this collision locus, the attractor
and the horseshoe may merge in a two-sided Lorenz attractor, or they may
exchange their nature: the Lorenz attractor expel the singular point sigma and
becomes a horseshoe and the horseshoe absorbs sigma becoming a Lorenz
attractor.
  By crossing this collision locus, the attractor and the horseshoe may merge
in a two-sided Lorenz attractor, or they may exchange their nature: the Lorenz
attractor expel the singular point sigma and becomes a horseshoe and the
horseshoe absorbs sigma becoming a Lorenz attractor.
