  The measurement of Zeeman splitting in spectral lines---both in emission and
absorption---can provide direct estimates of the magnetic field strength and
direction in atomic and molecular clouds, both in our own Milky Way and in
external galaxies. This method will probe the magnetic field in the warm and
cold neutral components of the interstellar medium, providing a complement to
the extensive SKA Faraday studies planning to probe the field in the ionized
components.
