Remembering the order of events is critical for everyday functioning. For instance, during a traffic accident it is important to know and to remember whether the traffic light turned from red to green or from green to red. Our ability to track temporal order generally declines with age, and is impaired in patients with neurodegenerative diseases, such as Alzheimer disease. What brain mechanisms support the capacity to encode temporal order? To find out the answer, we combine behavioural testing with non-invasive magnetoencephalographic recordings, and direct recordings from the brains of pre-surgical epilepsy patients. Our working hypothesis is that the hippocampus, a deep structure in the middle of the brain, plays a critical role in encoding temporal context but also the temporal order of events. We hope our studies will help elucidate the mechanism by which we keep track of order and to shed into treatment of memory dysfunction due to injury and neurodegenerative diseases.