Grow an ice crystal from the real Nakaya diagram: temperature and supersaturation decide its habit — plates, needles, columns, sectored plates or fern-like dendrites. Vapour is consumed by the crystal, so growth stalls as the air around it dries, just like in a real cloud chamber. Reset and re-grow to compare crystals.
Habit follows the Nakaya / Kobayashi diagram: plates near −2°C and −12…−16°C, needles at −5°C, hollow columns at −8°C and −22…−25°C; higher supersaturation drives branching from plates into sectored plates then dendrites. Growth is diffusion-limited: the crystal consumes local water vapour, so the effective supersaturation falls and growth stalls — the same depletion that creates the characteristic fern shape. Six-fold symmetry arranges the arms at 60°.