Bones, symphonies and databases all rely on the same trick of nesting
A bone's toughness starts with microscopic collagen fibrils, bundled into ever larger layers of protein and mineral. A symphony is built the same way, from motifs to phrases to movements. Structure, the arrangement of related parts, turns up everywhere, and a hierarchy of small units inside bigger ones is its favourite pattern.
In the broadest sense a structure is an organised arrangement of connected elements, or the thing so arranged. It can be physical, like a machine, a mineral or an organism, or abstract, like a piece of software or a musical form. The connections take a few basic shapes: a hierarchy, where one element branches into many; a network, where many link to many; and a lattice, where each part connects to its neighbours in space.
Load-bearing structures range from skyscrapers and aircraft to anthills, beaver dams and salt domes. Engineers sort their parts by dimension. Ropes, beams and arches are treated as one-dimensional because their length dwarfs everything else; plates, shells and vaults are two-dimensional; solid masses are three-dimensional, and such heavy blocks were the main option for early builders at sites like Chichen Itza. Most everyday frameworks rely on beams that resist bending, while trusses, cable nets and shells spread forces in other ways.
Living things are layered from the start: cells form tissues, tissues form organs. Proteins have four levels of their own, beginning with a chain of amino acids that coils into helices and pleated sheets before folding into a working shape. Crystals repeat a basic unit cell, and mathematicians have shown there are exactly 230 possible ways, called space groups, for such a pattern to be symmetrical.
Music and computing borrow the same logic. Classical composers from 1600 to 1900 often paired an opening phrase with an answering one, punctuated by cadences like commas and full stops. Hierarchy helps listeners follow and remember a piece, though John Cage's work shows it is optional. Programmers build everything from two basics, arrays that allow instant lookup and linked lists that can grow or shrink, then stack them into queues, trees and hash tables.
Source: Structure
