$K\to \pi {\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$: Status and update

$K\to \pi {\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ decays, $\mathrm{\ell }=e,\mu$, will be one of the goals of future kaon facilities, like NA62 (CERN) and K${}^0$TO (J-PARC). We review briefly the theoretical status of those processes.