Mist or Fog?

I woke up to a particularly foggy morning in Norfolk today..or did I? Someone asked me later today the difference between 'fog' and 'mist' and I must admit, standing at the bus stop waiting for my bus, I didn't have a clue! It's been on my mind all day, so let's get to the bottom of it. The most substantial difference between the two is visibility. If your visibility is less than a kilometer, then it's 'fog.' If it's more than a kilometer, then it's 'mist'. I have checked this with a few of my books and each one states the same. If you actually compare the components that make up either 'fog' and 'mist', then they are basically the same thing: a 'suspension of water particles in the air by the cooling of air.'