  The discovery of thousands of exoplanets over the last couple of decades has
shown that the birth of planets is a very efficient process in nature. Theories
invoke a multitude of mechanisms to describe the assembly of planets in the
disks around pre-main-sequence stars, but observational constraints have been
sparse on account of insufficient sensitivity and resolution. Understanding how
planets form and interact with their parental disk is crucial also to
illuminate the main characteristics of a large portion of the full population
of planets that is inaccessible to current and near-future observations. This
White Paper describes some of the main issues for our current understanding of
the formation and evolution of planets, and the critical contribution expected
in this field by the Next Generation Very Large Array.
