"Since each snowflake faces a different turbulent path
through the atmosphere, each twist, turn and fall grants it a unique
symmetry. But if you subtract nature’s volatility from the equation,
then these icy flowers are no longer guaranteed uniqueness.

By
placing two crystal seeds next to each other and growing them under the
exact same conditions, Dr. Libbrecht found that he could create two
snowflakes with nearly the same intricate shapes and patterns."