This episode looks at snow, that most fleeting and beautiful of elements which endlessly fascinates us. Using rare footage we journey into the microscopically small world of the snow crystal, finding out how a snowflake forms and why it is always six-sided. The science of snow tests British Rail's claim that the snow that crippled their rolling stock in 1991 really was the 'wrong type of snow', and explains how a British company is the world's biggest producer of snow.
