This chapter explores the evolving complex identity of the European Union, tracing its origins to the principle of relational recognition and the early European Communities. It highlights how limits and openness shape integration, with national constitutions embracing ‘mutual embedded openness’ towards European Law. The same openness towards the Other is found in the Schuman Declaration. The limits are represented by respect for the Law against any delirium of dictatorial omnipotence. The EU’s legal order develops through dialogue and tension between national and supranational identities, favouring constitutional tolerance and cross-fertilisation over absolute supremacy. After the CJEU’s early landmark judgments in Van Gend en Loos and Costa v. ENEL, and a significant period of silence, case law, such as the Solange and controlimiti doctrines, established porous boundaries and fostered dialogical engagement between the Court of Justice of the European Union and national courts.