MLExplain is a step-by-step interpreter for OCaml that enables the user to inspect both their program’s state and the interpreter’s state itself. This interpreter is derived from JExplain, a step-by-step interpreter for JavaScript. The original goal of this work is to show that JSExplain can easily be reused with another language. MLExplain also aims to provide the user with a better understanding of the semantics of OCaml.