t = 0.0 s · adrenaline molecules = 0
⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.
This simulation renders a stylized 3D circulatory system — a beating heart, branching vessels and five target organs (brain/eyes, lungs, liver, gut, skeletal muscle) — and lets you trigger a real sympathetic "fight-or-flight" event. Click "Trigger fright" and gold adrenaline-molecule particles spawn at the adrenal glands and stream through the bloodstream to every organ: the heart beats faster and glows, pupils dilate, the liver lights up as it releases glucose, lungs pulse faster, and the blood-flow particle stream visibly shifts from the gut toward skeletal muscle. Adjust fright intensity and time speed, then watch — or fast-forward — the multi-minute real recovery as everything eases back to baseline. Orbit, zoom and pan freely to inspect the vessel network from any angle.