Hooke kept a square of black velvet outside so that it would stay cold. When it snowed during the daytime, he would take his microscope outside and spread the velvet out on the stage and peer at any snowflakes that happened to fall on it. Daniel saw, as Hooke did, that each one was unique. But again Hooke saw something Daniel missed: 'in any particular snowflake, all six arms are the same – why does this happen? Why shouldn't each of the six arms develop in a different and unique shape?'