Snowflake in the same micro-environment does not guarantee that each arm grow the same; indeed, for some crystal forms it does not because the underlying crystal growth mechanism also affects how fast each surface region of a crystal grows. Empirical studies suggest less than 0.1% of snowflakes exhibit the ideal six-fold symmetric shape. Very occasionally twelve branched snowflakes are observed; they maintain the six-fold symmetry. Snowflakes form in a wide variety of intricate shapes, leading to the notion that "no two are alike". Although nearly-identical snowflakes have been made in laboratory, they are very unlikely to be found in nature. Initial
How Do They Do It? series, presented by Robert Llewellyn. This version was released on DVD in the UK in May 2010. In the United States, the series airs on the Science Channel and is narrated by Chris Broyles. This programme is similar to the popular Canadian-produced documentary programme, "How It's Made", also broadcast on Discovery Channel networks. Episodes in the first season aired with 60-minute runtimes (including commercials). Episodes in the second season aired with 30-minute runtimes (including commercials). Episodes 60 minutes long taken the best from series 3 and 4 Each episode is 30 minutes long and airs on terrestrial UK channel five.