Like it happened for digital media and the web, the metaverse is poised to occupy a highly relevant place in the life of billions of people. Its development path, however, is not clear yet, as the setting of many variables, such as technologies, business models, and standards are still open questions. This paper addresses the issue of metaverse standards taking as example the approach adopted by the MPAI Metaverse Model (MPAI-MMM) recently published by Moving Picture, Audio, and Data Coding (MPAI). MPAI has attacked the metaverse standardisation problem starting from an initial subset of functional requirements required by a significant number of application domains with the intention of gradually adding more functionalities as more applications are added. The paper describes the main steps that have led to the development of the standard starting from the analysis of the potential domains of application and the specification method. Then it explores the MMM main components: the Processes performing Actions on Items, the specification of Profiles, and the verification of the usability of the standard.