The distinction between lexical and functional elements plays a major role in current research in syntax and neighboring aspects of the study of language. In this article, we review the motivations of a progressive shift of emphasis from lexical to functional elements in syntactic research: the identification of the functional lexicon as the locus of the triggering of syntactic actions and of syntactic variation, and the description and analysis of the complexity of functional structures in cartographic studies. The latter point leads us to illustrate current cartographic research and to present the maps created in the study of clauses and phrases. The maps of CP, IP, and other phrasal categories all involve a richly articulated functional sequence. We then address issues of the numerosity and typology of the functional lexicon, the constraints on the featural specifications of possible functional heads, and the relations between cartographic research and minimalism.