  Nuclear fission represents the ultimate test for microscopic theories of
nuclear structure and reactions. Fission is a large-amplitude, time-dependent
phenomenon taking place in a self-bound, strongly-interacting many-body system.
It should, at least in principle, emerge from the complex interactions of
nucleons within the nucleus. The goal of microscopic theories is to build a
consistent and predictive theory of nuclear fission by using as only
ingredients protons and neutrons, nuclear forces and quantum many-body methods.
Thanks to a constant increase in computing power, such a goal has never seemed
more within reach. This chapter gives an overview both of the set of techniques
used in microscopic theory to describe the fission process and of some recent
successes achieved by this class of methods.
