  The results on the photo- and electroexcitation amplitudes of most nucleon
resonances in the mass range up to 2.0 GeV determined from the CLAS
experimental data on exclusive $\pi^+\pi^-p$ photo-/electroproduction off
protons in collaboration between the Jefferson Lab and Moscow State University
are presented. The first and only available results on electroexcitation
amplitudes from CLAS in a wide range of photon virtualities $Q^2$ $<$ 5.0
GeV$^2$ revealed the nucleon resonance structure as a complex interplay between
the inner core of three dressed quarks and external meson-baryon cloud. These
results shed light on the strong QCD dynamics which underlines the generation
of excited nucleon states of different structural features from confined quarks
and gluons. The future prospects of these studies in the new era of experiments
with the CLAS12 detector, which started successfully in Spring of 2018, are
outlined.

Nuclear Experiment;High Energy Physics - Phenomenology