My research explores the fundamental building blocks that make up human languages, how these building blocks relate to each other and how languages of the world differ in this respect. I pursue this research focusing on two major empirical domains: traditional grammatical categories and categories belonging to the language of interaction which I hypothesize is also constrained by grammar. In my 2014 monograph, I develop a framework for discovering and comparing grammatical categories across languages. This work was inspired by 15 years of fieldwork on two languages indigenous to North America (Halkomelem, Blackfoot). It seeks to reconcile a tension between two opposing views: Typologists observe that languages differ in their categorial inventories but generative linguists assume that there is a core which all languages share, including a set of universal categories. The key to reconciling this tension, I argue, is to assume that the categories we observe are always constructed on a language-specific basis, but that there are some universal building blocks involved in their construction, namely the universal spine, a hierarchically organized set of functions which is at the core of constructing sentential meanings. I have since used this framework to explore an empirical domain which lies outside of what traditional grammars and modern linguistic theory have considered, namely the language of interaction. When embedded in a conversation, sentences are enriched with elements that serve to manage interaction (e.g., particles like hm, oh, and sentence intonation). My research has revealed that the linguistic behavior of these elements – their universal and their language-specific properties – can be explained in much the same way as that of grammatical categories of the traditional type. Thus, my research links to neighboring fields, including philosophy (referential semantics, pragmatics), sociology (conversation analysis), and psychology (theory of mind).