This paper discusses the existence of X-within-X structures in language. Constraints to same-category embedding have been the focus in a number of recent studies. These studies follow a long-standing tradition in linguistic theory that assumes a ban on the adjacency of same-category elements. In the present work, data drawn from a typologically broad variety of languages suggest that the postulated constraints are not so robust. It is shown that X-within-X structures do exist in language. In this context, an argument is made in favor of an unrestricted conceptualization of Merge, independent from category distributions, while recursion is taken to be a property of procedures and not of structures. The discussion of X-within-X patterns provides insights with respect to the attested category distributions, the nature of categories, and the language faculty, from a biologically plausible point of view.