We here round off a book on biophysical foundations and computational modeling of electric and magnetic signals in the brain. We summarize some key insights from such modeling, and we clear up some common misconceptions about extracellular potentials. We address the main limitations with the standard modeling framework used to compute extracellular potentials, discussing the uncertainty in model parameters and its neglect of ephaptic interactions between active neurons. We identify what we believe are key areas of future applications and give an outlook for future modeling challenges.