Biohackers chasing the fountain of youth are turning to an unlikely new tool: nicotine. Once demonized for its role in cigarettes, the addictive stimulant is now being recast as a cognitive enhancer with potential anti-aging perks. But don’t go reaching for a pack of smokes just yet. Longevity fanatics say you’ll only get the perks if you use it the right way — get it wrong, and you could get burned. Here’s everything you need to know. What is nicotine? Nicotine is a naturally occurring