This is a diagram of the Glymphatic system. The Glymphatic system helps to clean the brain of it's waste products while we sleep. It could be that this is one of the main reasons why we need to sleep.
Matthew is one of the world's experts on sleep.
The short version of how the brain clears out waste when we sleep.
Dr. Maiken Nedergaards explains the glympatic system in more detail in this great presentation.
It was only recently discovered that lymphatic vessels do go into the brain.
The video above is a bit dry. This one is a bit more entertaining.