A critical challenge for nuclear theory is the quest for the universal
energy density functional, which will be able to describe properties of
finite nuclei (static properties, collective states, large-amplitude
collective motion) as well as extended asymmetric nucleonic matter
(e.g., as found in neutron stars). Self-consistent methods based on the
density functional theory have already achieved a level of sophistication
and precision which allows analyses of experimental data for a wide range
of properties and for arbitrarily heavy nuclei. Developing a universal
nuclear density functional will require a better understanding of the
density dependence, isospin effects, and pairing, as well as an improved
treatment of symmetry breaking effects and many-body correlations.