  The isovector--vector and the isovector--axial-vector current are related by
a chiral transformation. These currents can be called chiral partners at the
fundamental level. In a world where chiral symmetry was not broken, the
corresponding current-current correlators would show the same spectral
information. In the real world chiral symmetry is spontaneously broken. A
prominent peak -- the rho-meson -- shows up in the vector spectrum (measured in
(e^+ e^-)-collisions and tau-decays). On the other hand, in the axial-vector
spectrum a broad bump appears -- the a_1-meson (also accessible in tau-decays).
It is tempting to call rho and a_1 chiral partners at the hadronic level.
Strong indications are brought forward that these ``chiral partners'' do not
only differ in mass but even in their nature: The rho-meson appears dominantly
as a quark-antiquark state with small modifications from an attractive
pion-pion interaction. The a_1-meson, on the other hand, can be understood as a
meson-molecule state mainly formed by the attractive interaction between pion
and rho-meson. A key issue here is that the meson-meson interactions are fixed
by chiral symmetry breaking. It is demonstrated that one can understand the
vector and the axial-vector spectrum very well within this interpretation. It
is also shown that the opposite cases, namely rho as a pion-pion molecule or
a_1 as a quark-antiquark state lead to less satisfying results. Finally
speculations on possible in-medium changes of hadron properties are presented.
