This is a fascinating question so I asked my friends about it and this is what they came up with.
Look at your collection. Do they come from something that was living or not living? Think about clouds are they like all the other living things that you see around you? Are they like trees, are they like your pets, are they like the flies and other insects that annoy you? You must have questions, ask them, go to
Think about the things that you have collected.