This chapter describes the historical development of Systemic Functional Linguistics (SFL), with an emphasis on the influential work of Michael A.K. Halliday. SFL emerged as an alternative to the prevailing theories of language study, positing a multi-dimensional approach that considers the form, function, and context of language. Over the years, SFL has evolved to integrate phonology, expand its metafunctions, and adapt to new areas of study. Specifically, the contributions assembled in this special issue demonstrate the diverse range of contemporary research inspired by SFL. Applications of SFL have extended to L2 language teaching and learning, as well as to the analysis of interpersonal features in news reporting. Furthermore, the study of phonology in SFL has progressed with updated analyses challenging conventional assumptions about the relationships between clauses and tone groups.