  Cosmology is usually understood as an observational science, where
experimentation plays no role. It is interesting, nevertheless, to change this
perspective addressing the following question: what should we do to create a
universe, in a laboratory? It appears, in fact, that this is, in principle,
possible according to at least two different paradigms; both allow to
circumvent singularity theorems, i.e. the necessity of singularities in the
past of inflating domains which have the required properties to generate a
universe similar to ours. The first of them is substantially classical, and is
built up considering solitons which collide with surrounding topological
defects, generating an inflationary domain of space-time. The second is,
instead, partly quantum and considers the possibility of tunnelling of
past-non-singular regions of spacetime into an inflating universe, following a
well-known instanton proposal.
  We are, here, going to review some of these models, as well as highlight
possible extensions, generalizations and the open issues (as for instance the
detectability of child universes and the properties of quantum tunnelling
processes) that still affect the description of their dynamics. In doing so we
will remark how the works on this subject can represent virtual laboratories to
test the role that fundamental principles of physics (particularly, the
interplay of quantum and general relativistic realms) played in the formation
of our universe.
