Memory makes us. If we couldn't recall the who, what, where, and when of our everyday lives, we wouldn't be able to function. We mull over ideas in the present with our short-term (or working) memory, while we store past events and learned meanings in our long-term (episodic or semantic) memory. What's more, memory is malleable–and it tends to decay with age. So stay sharp by learning about the science of recollection.