This paper is a concise review of the physics of structures. The progress of the structure theory was motivated by the appearances of many different ordered structures that are self-organized through spontaneous dynamics. These observations impressed on us that our physics interest has been forwarded far from the classical orders of the maximized entropy. For typical examples in plasma physics, cited are the MHD equilibria (Taylor relaxed state), the ion acoustic solitons, and the van Kampen modes of continuous-spectrum Langmuir waves. The MHD equilibria and the solitons are examples of structures self-organized in dissipative dynamical systems, while the van Kampen modes are of a different physics structure. The third example is cited to distinguish the self-organization phenomena in dissipative systems and the echo phenomena in conservative systems. A static theory for the intrinsic structures is developed to clarify the basic difference between the classical orders and the self-organized structures. In linear models, an intrinsic structure is characterized by a singular spectrum of a certain eigenvalue problem. The Taylor relaxed state is characterized by the continuum of the point spectra of the rotational operator. The general MHD equilibrium is related to a nonlinear eigenvalue problem. The soliton is a nonlinear eigenfunction of the Helmholtz-type Bohm equation. The variational expression of an intrinsic structure is characterized by restrictive functionals, which, in a dynamical theory, is related to selective conservations. The principle of the selective dissipations and conservations in relaxations provides a dynamical characterization of the self-organization. The Taylor relaxed state is obtained by minimizing the, magnetic-field energy with conserving the magnetic helicity. This selective dissipation occurs in the fluctuations of kink modes. The soliton is self-organized by the dissipation of the Hamiltonian with keeping the energy approximately constant. The principle of the selective dissipation is logically a generalization of the ergodic hypothesis for the classical order. The selective dissipation could be proved in a rigorous way by analyzing the attractor of the dynamical systems (semigroups), just as the proof the ergodic theorem is obtained by the time-asymptotic analysis of a class of semigroups.
