Beans
Fabaceae · 19,500 species · 11 chromosomes

The most
useful seed
on Earth

A bean is a packet of starch and protein wrapped in a waterproof coat, carrying a complete miniature plant and a chemical arsenal meant to stop you eating it. This is a field guide to what is actually inside one.

Open the seed → Browse 34 species
Wild ancestor
Phaseolus vulgaris var. aborigineus
Domesticated
Twice, independently, ~8,000 BP
Genome
587 Mb · 27,197 genes
Red kidney bean
Drag to rotate, scroll to zoom. Geometry is generated from each species' real length : width : thickness ratio — the kidney outline appears whenever the seed's spine curves faster than its cross-section shrinks.
01 — Definitions

“Bean” is four different words

Botany, agriculture, cooking and marketing each use it to mean something else, and none of them agree. Pick a category to see what it actually excludes.

Legume

17kJ/gGross energy of dry bean matter by bomb calorimetry — about the same as wheat, and a third of pure fat
941kJ/molBond energy of N≡N, the triple bond a root nodule breaks at ambient temperature and pressure
70khauPhytohaemagglutinin in a raw red kidney bean. Ten minutes at a rolling boil takes it below 400
0.4kg CO₂eEmissions per 100 g of pea protein. The same protein from beef costs 50 kg
02 — Composition

What a dry bean is made of

Percent of dry matter in mature Phaseolus vulgaris. Hover or tap any band for what it does — and why two of them are the reason beans need cooking at all.

Proximate composition

% dry matter
03 — The guide

Seven ways in

Chapter one

History

Fourteen thousand years from wild fava at Ahihud to a patent fight over a yellow bean. Twenty scrollable moments, plus why Pythagoras banned them.

Timeline → Chapter two

Botany & anatomy

Testa, hilum, micropyle, cotyledon, radicle. An interactive section diagram, the family tree, and the nitrogenase reaction drawn out step by step.

Dissect it → Chapter three

Chemistry

Phaseolin, stachyose, phytate, lectins, vicine, canavanine. The molecules that store the energy and the ones that defend it.

Molecules → Chapter four

Nutrition & energy

Where the calories come from, the amino-acid scoring model, and a slider that shows exactly why beans and rice complete each other.

Run the numbers → Chapter five

Varieties

Thirty-four species and market classes, filterable by genus, class and trait, each with full composition, seed dimensions and a 3D model.

Browse → Chapter six

Cooking science

Pectin, pH and pressure. An altitude calculator, the hard-to-cook defect, and an honest estimate of the gas.

Get them soft → Appendix

The data

Every number on this site in one sortable table, with production tonnages, environmental footprint and the sources behind each figure.

Open the table →
Warning

Four that can hurt you

Raw kidney beans, fava beans with G6PD deficiency, grass pea as a staple, and bitter lupin. Each has a real mechanism and a real dose.

Read the mechanisms →