Lighting up a cigarette sends a chemical signal racing to your brain in less time than it takes to read this sentence. That near-instant hit is exactly why smoking is one of the hardest habits to break, and one of the most damaging to the organ that controls everything you think, feel, and do. From…

Your brain starts changing within minutes of your first sip of alcohol, and the effects ripple through every part of how you think, move, and feel. More than 84% of adults report drinking alcohol at some point in their lives, which means understanding what happens inside the skull after that drink matters to almost everyone.…