 By far the two most popular approaches are string theory and loop quantum gravity. The former is an example of an approach to quantum gravity in which the gravitational field is not quantized; rather, a distinct theory is quantized which happens to coincide with general relativity at low energies. The latter is an approach involving (constrained) canonical quantization, albeit of a version of general relativity based on a different choice of variables than the usual geometrodynamical, metric-based variables. We cover the basic details of each of these in the following subsections.