  Studies of the nucleon resonance electroexcitation amplitudes in a wide range
of photon virtualities offer unique information on many facets of strong QCD
behind the generation of all prominent excited nucleon states. Advances in the
evaluation of resonance electroexcitation amplitudes from the data measured
with the CLAS detector and the future extension of these studies with the
CLAS12 detector at Jefferson Lab are presented. For the first time, analyses of
$\pi^0p$, $\pi^+n$, $\eta p$, and $\pi^+\pi^-p$ electroproduction off proton
channels have provided electroexcitation amplitudes of most resonances in the
mass range up to 1.8 GeV and at photon virtualities $Q^2 < 5$~GeV$^2$.Studies
of the resonance electroexcitation amplitudes revealed the $N^*$ structure as a
complex interplay between the inner core of three dressed quarks and the
external meson-baryon cloud. The successful description of the
$\Delta(1232)3/2^+$ and $N(1440)1/2^+$ electrocouplings achieved within the
Dyson-Schwinger Equation approach under a traceable connection to the QCD
Lagrangian and supported by the novel light front quark model demonstrated the
relevance of dressed quarks with dynamically generated masses as an active
structural component in baryons. Future experiments with the CLAS12 detector
will offer insight into the structure of all prominent resonances at the
highest photon virtualities, $Q^2 < 12$~GeV$^2$, ever achieved in exclusive
reactions, thus addressing the most challenging problems of the Standard Model
on the nature of hadron mass, quark-gluon confinement, and the emergence of
nucleon resonance structures from QCD. A search for new states of hadronic
matter, the so-called hybrid-baryons with glue as a structural component, will
complete the long term efforts on the resonance spectrum exploration.
