The paragraph compares the brain to the universe in three key ways:
1. They are both composed of intricate networks - the brain of neurons and neurotransmitters, and the universe of galaxies, planets, and galactic networks.
2. They are both held together by connecting forces - the brain by synapses between neurons, and the universe by dark matter.
3. They both contribute to our understanding and existence, and remain complex structures that are still being uncovered in their secrets.