These are astrocytes. Neurons get all the attention when it comes to brain cells, but there are other types of cell in there as well. Astrocytes are star-shaped cells that have long been considered "helper" cells with no functional purpose, but recent research has questioned that idea.
For example, here is an article on a study showing that astrocytes play a key role in the brain's timekeeping mechanisms. When these cells are disrupted in a mouse, it throws its whole day off, altering the timing of daily routines. As the articles says, they're real clock stars. Groan.
Sleep is a rhythm that affects us all, and astrocytes play a role in our daily shut-eye. As we've discussed before, astrocytes play a role in the brain's daily housekeeping mechanisms, and when we don't get enough sleep, they may kick into overdrive and cause the brain to "eat itself." Eww.
So you can thank astrocytes for your daily ups and downs. Have you noticed your cognitive performance peaking at a certain time of day? Is there a time when your mind suddenly gets foggy for a few hours? Cambridge Brain Sciences lets you identify those patterns with objective tests of your brain's performance, and I'd love to hear about what you're finding so far, so let me know in the comments.