The phase diagram is usually plotted and measured by two degrees of freedom, namely, pressure (P) and temperature (T). Our group has been devoting on adding another factor, light, into the phase diagram. By simply saying light cannot cover everything here, as it contains polarization, frequency, and duration, etc. Naively speaking, light excites electron carriers from the valence band to the conduction bands, giving an excited state. This is evaluated according to the imaginary part of dielectric function. Once a strong laser is irradiated, photon absorption might distroy the sample. On the other hand, if the imaginary part is zero, the light damage can be eliminated. Then the question is, how does the light interact with the system? Recently, our group has elucidated that this belongs to a second order (leading order) scattering process, akin to a frequency renormalized energy landscape under the ponderamotive picture. Hanli and I wrote a Perspective on JPC Letters (10.1021/acs.jpclett.4c03047) to review this mechanism. In addition, we perform anharmonic interaction dressed dielectric function of conventional (II-VI) semiconductors, such as MgS and MgSe. Phase transformation under terahertz light can be triggered, and we also propose a non-cutoff natural hyperbolic dispersion in wurtzite and hexagonal phases, in the terahertz regime. Our work just appears at Phys. Rev. Mater., at 10.1103/PhysRevMaterials.9.034602.