  We discuss various aspects of the description of branes as topological
solitons in unstable brane systems of higher dimensions. We first describe a
classification of all the possible realisations of branes of M and type II
theories as topological solitons of a brane-antibrane system. We then present a
description of type IIB NS-NS p-branes in terms of topological solitons in
systems of spacetime-filling NS9, anti-NS9 pairs and discuss the implications
of these constructions in the description of BPS and non-BPS states in the
strongly coupled Heterotic SO(32) theory. We finally present briefly the
construction of a conjectured spacetime-filling non-BPS M10-brane, starting
point for a brane descent construction of the branes of M-theory.
