This chapter outlines the phenomenological components of crypto-asset ecosystems. It introduces their foundational traits by exploring their underlying combination of technologies and the role played by various stakeholders and architectures. It sketches the background against which crypto-asset-related concepts were devised, starting from P2P transfers and tokenisation, to the advent of stablecoins and CBDCs. It defines crypto-asset ecosystems, highlighting the value of terminological disambiguation for what concerns crypto-assets and tokens. It explores the landscape of cryptocurrency transfers by deploying a teleological and accountability-based approach. It underlines the nature of crypto-asset ecosystems as ecosystems of interconnected socio-technical ecosystems, and the need to focus not only on the interplay of their components but also on corresponding developments in terms of non-centralisation and disintermediation. Finally, it outlines methodology benchmarks to address crypto-asset ecosystems from a regulatory perspective while heeding conceptual, ideological, and technical evolutions.