The electric field in numerical human models has been used as an evaluation metric in the last 30 years. Recently, multiphysics, multi-scale modeling, and fast computation methods have advanced the state of the art in electrostimulation. These methods combined with image processing and machine learning are expected to bring personalized medicine in the near future. In this review, we presented two examples of electrostimulation; nerve root stimulation and brain stimulation. For the latter example, machine learning is demonstrated to successfully estimate the induced electric field in the brain.