  We consider the lightest scalar meson in the frame of the $SU_L(2)\times
SU_R(2)$ linear $\sigma$ model, keeping in mind that this model could be the
low energy realization of the two-flavour QCD. We show that the $\sigma$ field
is described by its four-quark component at least in the $\sigma$ resonance
energy (virtuality) region and the $\sigma\to\gamma\gamma$ decay is the four
quark transition.
  We emphasize that residues of the $\sigma$ pole in the $\pi\pi\to\pi\pi$ and
$\gamma\gamma\to\pi\pi$ amplitudes do not give an idea about the $\sigma$ meson
nature, and the progress in studying the $\sigma$ meson production mechanisms
in different processes could essentially further us in understanding its
nature.
