How snowflakes form and why two never look the same

(WHTM) --Now with Thanksgiving behind us and Christmas just a month away, everyone will be waiting for the snow to fall to make it a white Christmas.
But, what exactly is snow and how does it form? Also, why do two snowflakes never look alike?
According to the National Snow and Ice Data Center (NSIDC), snow is the accumulation of water vapor that turns into ice crystals. It is formed when the temperature in the atmosphere is at or below freezing. If the temperature near the ground is also at or