Inside us
Caffeine
A small molecule changes how your brain receives a signal for sleepiness.
Caffeine blocks adenosine receptors. It can make you feel more alert, but it does not erase your need for sleep.
A closer look
The picture, in three parts.
Absorb
Caffeine enters the bloodstream after you consume it.
Reach
It can cross into the brain.
Block
It competes at receptors normally activated by adenosine.
Where could this take you next?
Sources & further reading +
Short explanations, grounded in published sources. Follow the originals for depth and context.
Sources checked: 10 September 2026. Visuals are illustrations, not documentary evidence.
Our approach to sources and corrections