What caffeine does to your body and brain

Many of us can't start our day without a jolt of caffeine.

Various caffeinated drinks affect your health in different ways - a new study shows coffee seems to be associated with longer life, while many energy drinks have surprisingly high sugar levels.

Caffeine itself is a stimulant with some positive and negative effects. It makes most of us feel more alert, awake, and focused, but too much can also backfire.

It also affects a host of processes in our bodies, including our digestion, metabolism, and vision.

Here's what's really going on after you drink a cup of joe.