What is life?

"What is life? It is the flash of a firefly in the night. It is the breath of a buffalo in the wintertime. It is in the little shadow which runs across the grass and loses itself at sunset." - Crowfoot Blackfeet

Just started to read "Short Nights of the Shadow Catcher" by Timothy Egan, about the life and photographs of Edward Curtis.  The book opens with this quote, and I really like it.  I'm not sure what I think life is, but this provides a stirring image.