Book excerpt: Glass is out of equilibrium and reduces into an equilibrium solid. This whole process is a thermodynamical phase transition, while the so-called glass transition is an observable transition with no changes in structure. We describe that the glass transition is a purely kinetic phenomenon due to strong fluctuations in molecular configurations in supercooled liquid. Intermediate-range orders (IROs) have important roles on the glass transition process which is explained by the embryo and freezing of IROs. We conclude that the glass transition is an emergence of a new system of glass in a nonequilibrium state and a glass is a nanomaterial which is composed of a periodic nano-structure of IROs. The mean field theory introduced the random first order transition (RFOT) as the ideal glass transition which prevents the Kauzmann paradox. Recently, an ideal glass was realized using silicate glass during long aging below the Kauzmann temperature. An ideal glass is a nanomaterial which is composed of a periodic nano-structure of intermediate-range orders in an amorphous phase. The results identified the (spontaneous) dissipative structure as an equilibrium state of an ideal glass. An ideal glass is a temporal steady state toward the ground state of materials, which is a polycrystal.