The electric (${alpha}_{pi}$) and the magnetic (${beta}_{pi}$) polarisabilities are fundamental properties of the pion characterising the rigidity of its internal structure. They have been precisely measured at the COMPASS experiment at CERN with a ${pi}^{-}$ beam of 190~GeV/c assuming ${alpha}_{pi}+{beta}_{pi}=0$. Muons of the same momentum were used for controlling of systematic effects. The obtained result ${alpha}_{pi}=-{beta}_{pi}=(2.0pm 0.6_{stat.}pm 0.7_{syst.})times 10^{-4} fm^3$ is in agreement with the prediction of the Chiral Perturbation Theory.
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