The green box contains a brand new rat neuron. Why is this important? Well, until quite recently researchers were unsure of two things: whether it's possible for the brain to change and whether it can grow new cells. With the help of rats and monks, the answer is emerging: quite possibly yes.
This phenomenon is called neuroplasticity and is all the rage in neuropsychology at the moment. As none of us are getting any younger, it's good to know our brains still have the capacity for change.