  Photo- and electroproduction of pions and eta-mesons is studied on the
nucleon. The formalism of such reactions is presented including polarization
degrees of freedom and theoretical approaches are discussed. In particular, the
threshold and $\Delta$-resonance region of pion photoproduction is considered
and recent developments on low energy theorems (LET) and the E2/C2 quadrupole
excitation of the $\Delta$ are presented. For eta photoproduction we show our
calculations for the threshold region of the new Mainz experiment and
demonstrate the sensitivity of this reaction to the elementary $\eta NN$
coupling and the resonance parameters of the $S_{11}(1535)$. In nuclear
applications we point out the importance and advantage of light nuclei as $d$,
$^3H$, $^3He$ and $^4He$ for the isospin structure of the reactions as well as
for medium effects of the nucleon resonances.
