The last decades have seen important progress in the economic analysis of institutions, with increasing concern about the need to ‘unbundle’ this concept and the diversity of situations it covers. It is so because of the complexity of the systems the concept intends to capture and the ambiguity of definitions often perceived as catch-all ideas without a clear connection to a research strategy. This essay contributes to the literature emphasising that overcoming these difficulties requires a theoretical framework identifying and characterising distinct institutional layers. The content of this framework is substantiated through the analysis of the nature and role of the long-ignored intermediate layer of ‘meso-institutions’. Meso-institutions designate devices and transmission mechanisms linking general rules, norms and beliefs established at the macro-institutional level with their perception, adaptation, and implementation (or challenge) by the actors populating the micro-level. Operationalising this framework relies on a research strategy that proceeds from a ‘substantive theory’ of institutions to the collection and processing of ‘empirical evidences’ through the development of ‘auxiliary theories’ designed to capture specific institutional objects. References to several empirical studies support the relevance of this approach.