In this article, Vitalik directly addresses a specific technical aspect of a subproblem: how to more easily read from L2 to L1, from L1 to L2, or from one L2 to another L2. Solving this issue is crucial for achieving asset/key separation architecture, but it also has valuable use cases in other areas, most notably optimizing reliable cross-L2 calls, including use cases such as moving assets between L1 and L2.