  Partially ionised plasmas (PIP) constitute an essential ingredient of our
plasma universe. Historically, the physical effects associated with partial
ionisation were considered in astrophysical topics such as the interstellar
medium, molecular clouds, accretion disks and, later on, in solar physics. PIP
can be found in layers of the Sun's atmosphere as well as in solar structures
embedded within it. As a consequence, the dynamical behaviour of these layers
and structures is influenced by the different physical effects introduced by
partial ionisation.
  Here, rather than considering an exhaustive discussion of partially ionised
effects in the different layers and structures of the solar atmosphere, we
focus on solar prominences. The reason is that they represent a paradigmatic
case of a partially ionised solar plasma, confined and insulated by the
magnetic field, constituting an ideal environment to study the effects induced
by partial ionisation. We present the current knowledge about the effects of
partial ionisation in the global stability, mass cycle and dynamics of solar
prominences. We revise the identified observational signatures of partial
ionisation in prominences. We conclude with prospects for PIP research in
prominences, proposing the path for advancing in the prominence modelling and
theory and using new and upcoming instrumentation.
