  We review our work on the rho and sigma resonances derived from the Inverse
Amplitude Method. In particular, we study the leading 1/N_c behavior of the
resonances masses and widths and their evolution with changing m_pi. The 1/N_c
expansion gives a clear definition of quark-antiquark states, which is neatly
satisfied by the rho but not by the sigma, showing that its dominant component
is not quark-antiquark. The m_pi dependence of the resonance properties is
relevant to connect with lattice studies. We show that our predictions compare
well with some lattice results and we find that the rho-pi-pi coupling constant
is m_pi independent, in contrast with the sigma-pi-pi coupling, that shows a
strong m_pi dependence.
