  The strongly interacting Bose gas is one of the most fundamental paradigms of
quantum many-body physics and the subject of many experimental and theoretical
investigations. We review recent progress on strongly correlated Bose gases,
starting with a description of beyond mean-field corrections. We show that the
Efimov effect leads to non universal phenomena and to a metastability of the
low temperature Bose gas through three-body recombination to deeply bound
molecular states. We outline differences and similarities with ultracold Fermi
gases, discuss recent experiments on the unitary Bose gas, and finally present
a few perspectives for future research.
