  It is now clear that a binary formation pathway is responsible for a
significant fraction of planetary nebulae, and this increased sample of known
binaries means that we are now in a position to begin to constrain their
influence on the formation and evolution of their host nebulae. Here, we will
review current understanding of how binarity influences the resulting nebulae,
based on observations and modelling of both the central binary systems and the
planetary nebulae themselves. We will also highlight the most important
test-cases which have proved the most interesting in studying the evolution of
binaries into and through the planetary nebula phase.
