TongueClear

How does the tongue taste?
The tongue map in your school book is a myth, chilli heat is not a taste at all, and most of what you call flavour is really smell. Open up a 3D mouth, watch sugar, salt and glutamate dock on their receptors, and see why milk beats water after a bhut jolokia.

▶ Play with it  ·  Read the 60-second explainer  ·  Watch the 40-second video

In 60 seconds

1. A muscle covered in taste buds. The tongue is all muscle and no bone, moved by eight pairs of muscles. Its top is covered in papillae: filiform spikes for touch, and fungiform, foliate and circumvallate papillae that hide about 2,000 to 4,000 taste buds, each an onion of 50 to 150 cells.
2. Five tastes, five receptors. Sweet sugars clamp onto T1R2 + T1R3; umami glutamate onto T1R1 + T1R3. About 25 T2R receptors catch bitter, a warning sense. Sour protons flow in through the OTOP1 channel and salty sodium through ENaC. The brain reads the pattern across all five.
3. The tongue map is a myth. A 1901 study found small differences in sensitivity around the tongue's edge. A 1942 redrawing was misread as sweet only on the tip and bitter only at the back. Every area with taste buds senses all five; the middle is weaker only because it has few buds.
4. Chilli heat is pain. Capsaicin opens TRPV1, a heat sensor on nerve endings that normally opens above about 43 °C, so chilli feels hot. Menthol opens TRPM8, the cold sensor. The bhut jolokia passed a million Scoville units in 2007; milk and curd wash the oily capsaicin away far better than water.
5. Flavour is mostly smell. As you chew and breathe out, aroma flows from the back of the mouth up into the nose. Hold your nose and mango shrinks to sweet and a bit sour. Taste also needs saliva, and supertasters find some bitter chemicals far stronger.
6. Always renewing. Taste cells last about ten days on average and are replaced by stem cells, which is why a tongue scalded by hot tea usually recovers. Age, smoking, colds, COVID-19, medicines and a dry mouth can change taste; if it changes suddenly or does not come back, see a doctor.

Words worth knowing

Term	Meaning
Taste bud	An onion-shaped cluster of about 50 to 150 cells that detect taste chemicals dissolved in saliva.
Papillae	The small bumps on the tongue; filiform papillae sense touch, the other three kinds carry taste buds.
Receptor	A protein on a cell that catches one kind of chemical and switches the cell on.
Umami	The savoury taste of glutamate, found in tomatoes, dal, broth and cheese; named by Kikunae Ikeda in 1908.
Ion channel	A protein doorway in a cell’s skin; sour (OTOP1) and salty (ENaC) tastes work through channels.
TRPV1	A heat and pain sensor on nerve endings that opens above about 43 °C and with capsaicin from chillies.
Scoville heat unit	A measure of chilli heat; pure capsaicin is about 16 million SHU.
Retronasal smell	Smelling food from inside the mouth as air flows up into the nose; most of flavour.
Supertaster	A person who finds certain bitter chemicals, like PROP, very intense; about a quarter of people.

A short history

From Aristotle and the six rasas of Ayurveda to a myth-making tongue map, the discovery of umami, and receptors for every taste.

• 350 BCE · Aristotle lists the tastes (Aristotle, Athens, Greece)
• 100 BCE · Ayurveda names six rasas (The Charaka Samhita (compiled by physicians in the tradition of Agnivesha and Charaka), Ancient India)
• 1901 · Hänig measures the edge of the tongue (David P. Hänig, Leipzig, Germany)
• 1908 · Ikeda finds umami in kombu (Kikunae Ikeda, Tokyo Imperial University, Japan)
• 1912 · Scoville measures chilli heat (Wilbur Scoville, Detroit, USA)
• 1931 · The chemical some people cannot taste (Arthur Fox, DuPont laboratory, Wilmington, USA)
• 1974 · The tongue map is tested and fails (Virginia B. Collings, University of Pittsburgh, USA)
• 2001 · Sweet and umami receptors are pinned down (Greg Nelson, Charles Zuker, Nicholas Ryba and others, USA)

The full story, with 26 moments, charts, people and 46 sources: glassbox.how/e/tongueclear/history. The data lives in history.json.

Video and slides

Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.

File	What	Size
glassbox/reel.mp4	Reel / Short, with captions and soundtrack	1080×1920
glassbox/video.mp4	YouTube video, with captions and soundtrack	1920×1080
glassbox/slide-1…10.jpg	Instagram carousel	1080×1350
glassbox/thumb.jpg	YouTube thumbnail	1280×720
glassbox/cover.jpg	Share card and repo social preview	1200×630
glassbox/history-reel.mp4	“History in 10 moments” Reel / Short	1080×1920
glassbox/history-slide-*.jpg	History carousel	1080×1350
glassbox/post.json	Post copy and schedule used by the publish kit

Privacy

This box has no accounts and no ads, and it ships its own fonts and libraries. When you run it yourself it sends nothing anywhere. On glassbox.how, the site's /bar.js also loads Glassbox's analytics: Google Analytics to count visits (it asks first in the EU, UK and Switzerland, and stays off when your browser sends Global Privacy Control or Do Not Track) and ClickTrust to detect bots.

It remembers a few things in your own browser only, and never sends them anywhere:

Browser storage key	What it holds
tongueclear.v1	Which chapters you have opened, your best quiz scores, and sound on or off.

Exactly what each one sees is at glassbox.how/privacy.

Licences

• Code: MIT. Use it, change it, ship it.
• Explanations, text, images and videos (glassbox.json, glassbox/): CC BY 4.0. Credit “Glassbox, glassbox.how/e/tongueclear”.
• Third-party parts keep their own licences: three.js (MIT), Geist, Instrument Serif (SIL OFL 1.1).
• The Glassbox name and logo aren't covered by either licence. See the terms.

Found a mistake? Open an issue. Corrections happen in public.

Run it

It's plain HTML, CSS and JavaScript. No build step and no dependencies. Run locally, it contacts no other website.

python3 -m http.server 8000

Three.js and the fonts ship in vendor/ and fonts/, so it also works offline.

Then open http://localhost:8000.

How it's built

File	What
index.html, css/app.css	The page and its styles
js/app.js, js/stage.js, js/ui.js, js/kit.js	The shared Glassbox 3D engine: chapters, 3D stage, controls, quiz, video director
js/chapters/*.js	One file per chapter: the 3D model, controls, text, key terms, quiz and video scenes
js/tongue.js	The 3D mouth: a tongue surface with its four kinds of papillae, the muscles and nerves, teeth, palate, epiglottis and salivary glands, plus shared helpers
js/cells.js	The small-scale models: a taste bud cut open, the four papillae, a membrane with taste receptors and TRP channels, and ball-and-stick molecules
js/head.js	A side view of the head cut down the middle, for smell and flavour and for how the tongue moves
js/taste.js	The science and numbers: the five tastes and their receptors, foods, thresholds, the Scoville scale and TRPV1/TRPM8, with sources
glassbox.json	Title, question, explainer beats, key terms, browser storage and credits shown on glassbox.how
reel in each chapter	The storyboard the Glassbox studio records into short videos
glassbox/	The published video, slides, thumbnail and post copy
fonts/, vendor/three/	Self-hosted Geist and Instrument Serif (SIL OFL 1.1) and three.js (MIT)