Oftentimes, you can just study, in a very offhand (relaxed) way, the way something looks, observing it, and learn about it--for example, with walnuts, and the brain. They are very similar in appearance. That is, the whole walnut looks a lot like the brain. Carrots cut crosswise look like the eye....etc. Signatures in plants are small miracles, little treasure chests, not even locked!