  We study the electromagnetic form factor of the pion and kaons at
low-energies with the use of Chiral Perturbation Theory. The analysis is
performed within the three flavour framework and at next-to-next-to-leading
order. We explain carefully all the relevant consistency checks on the
expressions, present full analytical results for the pion form factor and
describe all the assumptions in the analysis. From the phenomenological point
of view we make use of our expression and the available data to obtain the
charge radius of the pion obtaining $<r^2 >_V^\pi=(0.452+-0.013) fm^2$, as well
as the low-energy constant $L_9^r(m_\rho)= (5.93+-0.43)10^{-3}$. We also obtain
experimental values for 3 combinations of order $p^6$ constants.
