  The Metaverse refers to a virtual-physical blended space in which multiple
users can concurrently interact with a unified computer-generated environment
and other users, which can be regarded as the next significant milestone of the
current cyberspace. This article primarily discusses the development and
challenges of the Metaverse. We first briefly describe the development of
cyberspace and the necessity of technology enablers. Accordingly, our bottom-up
approach highlights three critical technology enablers for the Metaverse:
networks, systems, and users. Also, we highlight a number of indispensable
issues, under technological and ecosystem perspectives, that build and sustain
the Metaverse.
