  We consider Andreev-Majorana (AM) bound states with zero energy on surfaces,
interfaces and vortices in different phases of the $p$-wave superfluids. We
discuss the chiral superfluid $^3$He-A, and time reversal invariant phases:
superfluid $^3$He-B, planar and polar phases. The AM zero modes are determined
by topology in bulk, and they disappear at the quantum phase transition from
the topological to non-topological state of the superfluid. The topology
demonstrates the interplay of dimensions. In particular, the zero-dimensional
Weyl points in chiral superfluids (the Berry phase monopoles in momentum space)
give rise to the one-dimensional Fermi arc of AM bound states on the surface
and to the one-dimensional flat band of AM modes in the vortex core. The
one-dimensional nodal line in the polar phase produces the two-dimensional flat
band of AM modes on the surface. The interplay of dimensions also connects the
AM states in superfluids with different dimensions. For example, the
topological properties of the spectrum of bound states in the three-dimensional
$^3$He-B is connected to the properties of the spectrum in the two-dimensional
planar phase (thin film).
