  Collectivity in ensembles of atoms gives rise to effects like super- and
subradiance. While superradiance is well studied and experimentally accessible,
subradiance remains elusive since it is difficult to track experimentally as
well as theoretically. Here we present a new type of phase transition in the
resonantly driven, open Dicke model that leads to a deterministic generation of
subradiant states. At the transition the system switches from a predominantly
superradiant to a predominantly subradiant state. Clear experimental signatures
for the effect are presented and entanglement properties are discussed. Letting
the system relax into the ground state generates a cascade of dark Dicke
states, with dark state populations up to unity. Furthermore we introduce a
collectivity measure that allows to quantify collective behavior.
