Did the Lisbon Treaty represent a turning point in national parliaments' roles within the European Union (EU)? 10 years after its entry into force, and after the EU has undergone significant changes, this book is the first lengthy publication that comprehensively assesses where national parliaments stand, both in a national and in a European perspective. To this end, it demonstrates how national parliaments increasingly interact with a growing number of EU institutions, and with their counterparts, and what functions these relationships fulfil. It also considers to what extent national parliaments have become 'Europeanised national institutions' actively involved in EU affairs on a domestic level, primarily on the basis of an analysis of the national parliaments of the largest EU Member States – France, Germany, Italy, Poland and Spain. Despite Brexit, the British Parliament too is examined where appropriate owing to its long-standing status as frontrunner in national parliaments' involvement in EU affairs. The book concludes that national parliaments have undoubtedly ceased to be absent from this field, as they have become much more actively engaged. Yet, some improvements remain necessary to ensure adequate levels of transparency, efficiency and sustainability, as well as to guarantee that engaging in EU affairs is attractive to national parliamentarians.