Every solid isa rule, repeating.
Nineteen structures, each one three lattice vectors and a handful of atoms — no data files, no downloads. Pick one and watch it assemble: from the motif that repeats, out to a crystal whose edges dissolve into fog.
Six families.
Nineteen ways to fill space.
The last column counts neighbours. It is the single most telling number about a structure — six means octahedral, twelve means closest packing, four means something is holding its bonds apart on purpose. Move through the list and the crystal behind these words follows you.
A crystal gets built four times over.
The viewer steps through these in order, and back again. Watch the background as you read — it is stepping with you, through rock salt.
Motif
The atoms that repeat, and nothing else — no box, no neighbours. For caesium chloride this is two atoms. That really is the whole structure; everything after it is bookkeeping.
Unit cell
Draw the box and atoms appear at all eight corners. They were always there — each corner atom belongs to eight cells at once, and you were only ever looking at one eighth of it.
Three by three by three
The first shell of neighbours arrives and coordination becomes something you can count rather than something you're told. This is the scale at which the family names in the index start to mean something.
Crystal
Repeat until the edges fall away into fog. Nothing new happens past this point, and that absence is exactly what a lattice is for.
Or grow it from a seed
The four stages above are a way of reading a structure. Growth is a different thing: a front advancing outward from a single nucleus, the camera falling back as it goes. That is how crystals actually form, and it is where the recursive, zooming-out feeling comes from — the recursion is in the process, not in the structure. A lattice is periodic, never self-similar; if you want true self-similarity in crystallography you want quasicrystals, or the branching of a snowflake.
Colour is a reading, not a finish.
Each mode answers a different question about the same atoms. The viewer switches between them without rebuilding anything, so you can hold a structure still and watch the meaning change.
Bring your own crystal.
Quartz, calcite, faujasite, ice — anything with coordinates too irregular to write down by hand needs a file. Drop a CIF and it gets parsed here in the browser: cell parameters read, symmetry operations applied to the asymmetric unit, bonds found by summed atomic radii.
One requirement. The file needs an explicit symmetry operation list — _symmetry_equiv_pos_as_xyz or _space_group_symop_operation_xyz. Both databases above include it. A file carrying only the space group name will be refused with a message rather than quietly rendering a fraction of the atoms.