For the thicker CP spacer, corresponding reflection spectra with EB are calculated in Fig. , showing the tunability of AFP resonant wavelength. In Fig. , AFP is further validated by experimentally measured the specular IR reflectance of EB thin film at 55° angle of incidence for two different polarization and compared with theoretical calculation by multilayer Fresnel Equation. The intrinsic tunability of CP's optical property and the metasurface geometry parameter space contain vast degrees of freedom, enabling us to design active thermoregulator with extraordinary performance and functionality. As shown in Figure , we designed and optimized the performance of the structure parameters by hybridizing meta-atoms, including the disk radii ( 𝑟 2 to 𝑟 0 ) and the thickness of CP spacer, which determine the AFP and GSP resonance absorption in the high emissivity state. The unit cell size of metasurface and the height of the Au disks were fixed at 10 μm and 150 nm, respectively. We then run the FDTD simulations to calculate the figure of merit (FOM) of the tunable metasurface emitter. The FOM is defined as the difference of the weighted average emissivity at two emissivity states with respect to blackbody at 34°C between 2.5 to 25 μm: