Research in our team focuses on the representation and processing of grammar, aiming to identify general principles governing grammatical learning, comprehension, and production across populations and languages. Our work adopts a cross-linguistic perspective and is grounded in cognitive science, integrating constructs from psycholinguistic theories that address the mechanisms underlying grammar use with constructs from linguistic theory that describe grammatical structure. Within this framework, we examine how grammatical processes are shaped by linguistic principles and learners’ linguistic experience. Using experimental methods, we study grammar in native and second-language learners, including linguistically diverse populations such as adult migrants, relying on behavioral measures both in the lab and in real classrooms, and, when relevant, neural indicators. This approach provides a strong foundation for investigating native grammatical processes as well as L2 learning mechanisms and teaching strategies, grounded in cognitive science and evidence-based research.