I love trees for many reasons. They have the greatest longevity of any living organism, as far as I know. They are wooden structures, but they are also alive, and they are machines doing work, albeit slowly. If you think about the time-scale of their activity and growth, you can recognize processes that are going on with them, like reaching for sunlight, roots feeling around for moisture and nutrients, etc. It's like looking at a snapshot and figuring out what the people in the photo are doing.