  We discuss ${\gamma}{\gamma}\to {\pi}{\pi}$ reactions, starting from the
two-pion threshold up to about $\sqrt{s_{{\gamma}{\gamma}}}$ = 6 GeV. We
include the dipion continuum due to pion exchange (for ${\pi}^+{\pi}^-$) and
${\rho}^\pm$ exchange (for ${\pi}^0{\pi}^0$) as well as the dipion
${\sigma}(600)$, $f_0(980)$ and $f_2(1270)$ s-channel resonances. We discuss
also a possible contribution of less pronounced scalar resonances $f_0(1500)$
and $f_0(1710)$ as well as the tensor resonances $f'_2(1525)$, $f_2(1565)$ and
$f_2(1950)$. We find that the inclusion of the spin-four $f_4(2050)$ resonant
state improves the situation at $\sqrt{s_{{\gamma}{\gamma}}} \approx$ 2 GeV. We
estimate the relevant diphoton partial decay width to be ${\Gamma}_{f_4 \to
{\gamma}{\gamma}} \approx$ 0.7 keV. At higher energies, Brodsky-Lepage and
hand-bag mechanisms are included in addition. We nicely describe the world data
for ${\gamma}{\gamma}\to {\pi}{\pi}$ for the first time both for the total
cross section and angular distributions.
  The cross section for the production of two-pions in ultraperipheral
ultrarelativistic heavy ion collisions is calculated in the impact parameter
space Equivalent Photon Approximation (EPA). We obtain the nuclear cross
section of 46.7 mb for ${\pi}^+{\pi}^-$ and 8.7 mb for ${\pi}^0{\pi}^0$ at the
LHC energy $\sqrt{s_{NN}} =$ 3.5 TeV and minimal cut on pion transverse
momentum $p_t>$ 0.2 GeV. Differential distributions in impact parameter, dipion
invariant mass, single pion and dipion rapidity, pion transverse momentum as
well as pion pseudorapidity are shown. The ${\gamma}{\gamma}\to {\pi}^+
{\pi}^-$ subprocess constitutes a background to $A A \to A {\rho}^0 (\to
{\pi}^+ {\pi}^-) A$ process.
