Present state of elementary particles to be specified by a set of quantum numbers is
summarized. An existence of four types of interactions between elementary particles is
reminded with an emphasis that not all particles are able of all four interactions. Those to be
able of strong interactions are named “hadrons”- compound of “quarks”. Compound from
quark-antiquark are “mesons” and compound from three quarks are baryons. Recently four,
even five quarks hadrons are confirmed experimentally, not to be in contradiction with QCD.
Nevertheless X,Y,Z particles are out of any classification into multiplets to be known for
standard mesons and baryons. Hadrons in interaction with charged leptons manifest space
structure to be called electromagnetic (EM) structure, first time revealed for protons before
the quark model of hadrons was established. It is described by “EM form factors (FFs)” the
number of which depends on spin of hadron. The Unitary and Analytic model of FFs is
presented to be based on analyticity and existence of vector-meson-resonances with quantum
numbers of photon. Model depends on some unknown coupling constant ratios. Therefore it is
applicable only to hadrons for which some experimental data exist. As a result only the EM
structure of the nonet of pseudoscalar mesons and the ½^+ octet baryons is completely
described in the framework of this model up to now.