Source analysis on the basis of scalp EEG, ideally with high density EEG, has been established as an imaging tool, which complements existing tools. In contrast to other techniques EEG-based imaging visualizes neuronal activity with a resolution of milliseconds, i.e. it is does not measure indirect consequences of epileptic activity such as blood flow changes or glucose consumption. Prospective studies showed that electric source localization localizes the focus correctly in the vast majority of patients who underwent surgical treatment. Up to now, in several hundreds of patients it was found: the likelihood to benefit from epilepsy surgery is 10x higher if the electrical source is removed together with the structural anomaly if that was not the case. Studies in operated patients and/or intracranial EEG could show that there is a high concordance between the calculated source and the intracranial focus. Other applications include the localization of vital cortex with evoked potentials. Overall, EEG-based imaging is relatively easily acquired and can be done also in children or other persons with limited collaboration capacities, can be combined with fMRI and is relatively cheap compared to other imaging tools. Possible future application could be the identification of epileptogenic activity in presumably normal EEG and network analysis, as well as network dysfunctions in other neurological and psychiatric diseases.