  The expansion of our universe, when followed backward in time, implies that
it emerged from a phase of huge density, the big bang. These stages are so
extreme that classical general relativity combined with matter theories is not
able to describe them properly, and one has to refer to quantum gravity. A
complete quantization of gravity has not yet been developed, but there are many
results about key properties to be expected. When applied to cosmology, a
consistent picture of the early universe arises which is free of the classical
pathologies and has implications for the generation of structure which are
potentially observable in the near future.
