<p>  The review covers the research and development of perpendicular media nanostructure focusing on the recording layer. The recording layer material includes the Co-alloys with hcp structure, the magnetic multilayers, and the alloys with ordered structures that have high magneto-crystalline anisotropies (K_u). The technologies of underlayer or interlayer for aligning the easy magnetization axis of magnetic crystal grain perpendicular to the film plane are briefly reviewed including the high K_u magnetic materials for future recording media. </p><p>  Observations of compositional and magnetization structures in sub-μm scale have played important roles in improving the recording layer. Typical data on these characteristics are explained in relation to the media structure improvements. Considering that high K_u magnetic materials will be employed in future recording media, basic experimental results related in controlling the easy magnetization axis and in keeping the surface flatness of L1₀-ordered magnetic materials are explained. Future possibilities for increasing the areal density beyond 1 Tb/in² by improving the magnetic material and the nanostructure of recording layer are also discussed.</p>