Electroencephalogram (EEG) represents one of the main tools to explore the brain. EEG signals are relatively simple to measure, but their interpretation is complex because activities generated by diverse sources converge at the site of the EEG sampling point, the recording electrode. We describe here the contribution of preclinical science to the understanding of EEG signals generated in physiological conditions and during brain disfunction with a specific focus on epilepsy. Different models and technologies and in vitro preparations utilized to identify the network determinants of EEG patterns are analyzed and discussed. Physiological and pathological oscillations at different frequency bands as well as the mechanisms of ictogenesis are also examined. We discuss here how the integrated and simultaneous study of the EEG with other experimental techniques, such as functional imaging, optogenetics, chemogenetics, and so on, contributes to a comprehensive understanding of brain activity and function. The EEG and experimental neurophysiology techniques represent cornerstones in brain research to unravel brain function and disease mechanisms.