LOGIC GATES
Seven digital-logic symbols — and how to build six of them from a single element, NAND
THE 9 MAJOR FOOD ALLERGENS
the foods US law singles out by name, and the two ways a label is allowed to say so
LANGUAGE FAMILIES
who is related to whom — on the numerals three and two in twenty-seven languages
DIVISIBILITY TESTS
what to read in a written number instead of dividing it: the tail, the digit sum and composite divisors
LEAP YEARS
one rule, a cycle of four hundred years and the ninety-seven extra days in it
MAMMALS IN TIME
from the first synapsid to us · 320 million years on one axis
VERTEBRATES IN TIME
when each group appeared · five hundred million years on one axis
BASIC PHYSICS FORMULAS
fifteen formulas · every letter explained beneath it
ANIMALS
the main branches — from comb jellies to chordates · who is actually related to whom
VERTEBRATES
from lamprey to bird · and why "fish" and "reptiles" are not groups