  Loop quantum cosmology predicts that quantum gravity effects resolve the
big-bang singularity and replace it by a cosmic bounce. Furthermore, loop
quantum cosmology can also modify the form of primordial cosmological
perturbations, for example by reducing power at large scales in inflationary
models or by suppressing the tensor-to-scalar ratio in the matter bounce
scenario; these two effects are potential observational tests for loop quantum
cosmology. In this article, I review these predictions and others, and also
briefly discuss three open problems in loop quantum cosmology: its relation to
loop quantum gravity, the trans-Planckian problem, and a possible transition
from a Lorentzian to a Euclidean space-time around the bounce point.
