  This article is a brief introduction to the rapidly evolving field of
many-body localization. Rather than giving an in-depth review of the subject,
our aspiration here is simply to introduce the problem and its general context,
outlining a few directions where notable progress has been achieved in recent
years. We hope that this will prepare the readers for the more specialized
articles appearing in the forthcoming dedicated volume of Annalen der Physik,
where these developments are discussed in more detail.
