  Presented is an overview of electromagnetic versions of the so-called X-type
waves intensively studied since their invention in early 1990.-ies in
ultrasonics. These waves may be extremely localized both laterally and
longitudinally and - what has been considered as most startling - propagate
superluminally without apparent spread. Spotlighted are the issues of the
relativistic causality, variety of mathematical description and possibilities
of practical applications of the waves.
