The terms "Web 3.0" and "Metaverse" now both refer to the third generation of the Internet. A theoretical framework for Web 3.0/Metaverse is constructed, which consists of three parts. The first part is the Web 3.0/Metaverse architecture, including the structure of the Internet at the Web 3.0/Metaverse system level and the structure of computers as the Internet end systems at the Web 3.0/Metaverse component level. The second part is the Web 3.0/Metaverse technology system, including nine Web 3.0/Metaverse technologies. The third part is the Web 3.0/Metaverse application world, which structurely integrates the virtual and real worlds into one and covers five fields, namely economy, politics, military, society, and culture, in either function or scene. A Web 3.0/Metaverse application system is a field or subsystem, or sub-subsystem, etc. of the Web 3.0/Metaverse application world. A kind of Web 3.0/Metaverse application, digital twinning, is analyzed. The first-principle of blockchain is proposed: in the Web 3.0/Metaverse application world, the core function of blockchain is to make contrust (common trust).

With the advances in technologies of artificial intelligence and 5G as well as the emerging concepts of blockchain and decentralized management, the next revolution of Internet, Web 3.0, has appeared. It will change the development of Internet and various professions and has thus attracted much attention from both academia and industry. This article analyzes the opportunities and challenges of Web 3.0. First, the differences among Web 1.0, Web 2.0, and Web 3.0 are elaborated, and the technical architecture of Web 3.0 is also studied. Second, through studying existing relevant literature, the current development status and the opportunities of Web 3.0 are summarized from both economic and technological aspects. Third, the challenges faced by Web 3.0 in research and regulation are pointed out. Finally, an outlook on the future development of Web 3.0 is given.

Blockchain is the key technology for Web 3.0 to build trusted interconnections and value interconnections. As a new decentralized infrastructure, the technology of blockchain is also constantly evolving. Combined with the background of Web 3.0, the technological progress and existing problems of blockchain are introduced in this paper, such as decentralized identity, smart contract, incentive mechanism, and privacy protection. They help to realize the technologies in Web 3.0, such as the data security sharing, business circulation and rights guarantee of users, so as to achieve the goal of more fair distribution and flow of the value.

Web 3.0 is the next important stage in the development of the Internet. China's 14th Five-Year Plan has proposed to accelerate digital development, cultivate and expand new industrial ecosystems such as blockchain, and take Web 3.0 as an important goal of the development of the digital economy. It is necessary to grasp the new opportunities of the new round of scientific and technological revolution and industrial transformation and promote rapid and healthy development of relevant strategic emerging industries in China. This article analyzes the development and application of Web 3.0, such as digital payment, NFT, blockchain games, etc. At the same time, this paper discusses the risks, regulatory policies, development paths and suggestions for developing Web 3.0 in China.

Web 3.0 is a frontier issue that deserves attention and involves a number of emerging areas such as the deep integration of human-machine and object networks, virtual-real integration and interaction, diverse business services, intelligent operation and maintenance management, and quantifiable security capabilities. It is difficult for the existing technical architecture to cope with the challenges. However, it is clear that the existing web paradigm is no longer able to support the development of Web 3.0 nor to meet the theoretical dilemma. Based on the fourth paradigm of network technology institutional development and the theory of multimodal network environment, this paper puts forward relevant proposals for building China's next-generation Internet, taking "co-ordinating the relationship between security and development" and achieving quantifiable design and verifiable metrics for network security as one of the key issues and core objectives. On this basis we propose to build an application-driven technology development path and establish an autonomous knowledge system in the field of network technology.

With the development of the information technology era, metaverse has gradually become the third internet revolution, and the metaverse terminal is an important component of it. This article describes the development trends and key technologies of the hardware part of the metaverse terminal in terms of micro displays, optical systems, and perceptual interactions. In terms of the micro display technology, two technologies, silicon based OLED and MicroLED, are mainly discussed; in terms of optical systems, the main topics discussed are surface relief grating waveguide technology, volume holographic waveguide technology, and metasurface waveguide technology; in terms of perceptual interaction, the interaction technology of gesture recognition and EEG recognition is mainly discussed.