What’s the most complex structure in the known universe? Hint: You’re using it right now to answer to this question. While you keep brainstorming, let’s discuss your cerebral cortex. This wrinkly, outermost layer surrounding your brain contains nearly 100 billion neurons, each of which has hundreds of thousands of synaptic connections. These connections enable you to think, perceive, and perform actions– like clicking the share button on this video so your friends can also expand their synaptic knowledge.