I think the song simply says that our brains are so complex that they're like universes inside our heads with trillions of things happening at once. Even though we can take advantage of these trillions of processes, most areas of the brain still aren't fully taken advantage of. Also, some people are so mentally lazy or become stuck in such simple life routines that they don't even attempt to exercise the parts of the mind that we know how to take advantage of.
I think the song simply says that our brains are so complex that they're like universes inside our heads with trillions of things happening at once. Even though we can take advantage of these trillions of processes, most areas of the brain still aren't fully taken advantage of. Also, some people are so mentally lazy or become stuck in such simple life routines that they don't even attempt to exercise the parts of the mind that we know how to take advantage of.