Unramified and finitely ramified henselian valued fields are central to studying model-theoretic phenomena in mixed characteristic. Decidability and definability in unramified henselian valued fields with perfect residue field are well understood, starting with the seminal work of Ax, Kochen, and Ershov. In this talk, we present recent developments in unramified henselian valued fields with imperfect residue field, and also comment on what changes in the case of finite ramification. This is joint work with Sylvy Anscombe.