  Although the inflationary paradigm is the most widely accepted explanation
for the current cosmological observations, it does not necessarily correspond
to what actually happened in the early stages of our Universe. To decide on
this issue, two paths can be followed: first, all the possible predictions it
makes must be derived thoroughly and compared with available data, and second,
all imaginable alternatives must be ruled out. Leaving the first task to all
other contributors of this volume, we concentrate here on the second option,
focusing on the bouncing alternatives and their consequences.
