This reminds me of ‘The Miniature Earth’ that I shared here: http://pairadimes.davidtruss.com/caring-across-the-curriculum/

I wonder what 7 billion grains of sand or rice would look like or weigh?

The biodiversity game on the site is also a great conversation starter: http://ngm.nationalgeographic.com/2011/01/seven-billion/biodiversity-game

So are the photos: http://ngm.nationalgeographic.com/2011/01/seven-billion/olson-photography ~Very powerful!