  In this article we give a precise description of the Plancherel decomposition
of the most continuous part of $L^{2}(Z)$ for a real spherical homogeneous
space $Z$. Our starting point is the recent construction of Bernstein morphisms
by Delorme, Knop, Kr\"otz and Schlichtkrull. The most continuous part
decomposes into a direct integral of unitary principal series representations.
We give an explicit construction of the $H$-invariant functionals on these
principal series. We show that for generic induction data the multiplicity
space equals the full space of $H$-invariant functionals. Finally, we determine
the inner products on the multiplicity spaces by refining the Maass-Selberg
relations.
