  Advances in the exploration of the spectrum and structure of the excited
states of the nucleon from experiments with electromagnetic probes on proton
targets are presented. Impressive progress has been achieved in the studies of
exclusive meson photoproduction in experiments with continuous electron beams
and with detectors of almost $4\pi$ acceptance. The high-quality data, coupled
with the advances in the amplitude analyses of exclusive photo- and
hadroproduction data, allow for the observation of several long-awaited new
baryon states known previously as the ``missing" resonances. Studies of
exclusive meson electroproduction in the resonance region with the CLAS
detector at JLab have provided the dominant part of the available world
information on exclusive meson electroproduction observables. These data offer
unique information on the structure of most well-established excited nucleon
states in the mass region up to 1.8~GeV in terms of the evolution of their
electroexcitation amplitudes with momentum transfer of the virtual photon. We
discuss the impact of these results on the insight into the strong interaction
dynamics that underlie the generation of the full spectrum of nucleon
resonances of distinctively different structure. These results shed light on
the emergence of hadron mass, which is one of the most important and still open
problems in the Standard Model. The extension of the nucleon resonance studies
in the experiments of the 12-GeV era at JLab with the CLAS12 detector are
outlined.
