  Full-spectrum ranging from sub 6 GHz to THz and visible light will be
exploited in 6G in order to reach unprecedented key-performance-indicators
(KPIs). However, extraordinary amount of energy will be consumed by network
infrastructure, while functions of massively deployed Internet of Everything
(IoE) devices are limited by embedded batteries. Therefore, energy
self-sustainable 6G is proposed in this article. First of all, it may achieve
network-wide energy efficiency by exploiting cell-free and airborne access
networks as well as by implementing intelligent holographic environments.
Secondly, by exploiting radio-frequency/visible light signals for providing
on-demand wireless power transfer (WPT) and for enabling passive backscatter
communication, ``zero-energy'' devices may become a reality. Furthermore, IoE
devices actively adapt their transceivers for better performance to a dynamic
environment. This article aims to provide a first glance at primary designing
principles of energy self-sustainable 6G.
