“For contextual remembering, new memories are related to existing memory content. This happens in a later stage of sleep, when we dream. As we sleep and try to follow our dream actions and experiences in the virtual space created by our brain, we often move our eyes rapidly. That’s why this stage of sleep is called rapid eye movement (REM) sleep. In REM sleep, the new memories uploaded in SWS are linked to past memory content, so it is not uncommon for us to wake up in the morning with new insights.23 We need to sleep and dream to be able to remember what we have experienced and thought in the long term.”