I was referred internally by a Mathworker. The overall process took about 3 weeks. I got a short phone talk with a manager first and scheduled the on-site 2 weeks later. First, it started off with a morning presentation about my PhD research, followed with 5 rounds of technical interview. The entire team was all PhD grads so the questions were more or less research orientated. Less coding challenges, unlike Google or Facebook, where their focus was coding ability. In general, the Mathworks' interviewers are more concerned about your talents, and potentials to grow (unless you are a very experienced candidate with 10+ year working history). So, prepare less on the technical details (e.g. how constructor works, or traverse a tree or even design pattern details), but focus on how you present yourself as a problem attacker who not only solvers questions but proposes new questions that aren't there before.