In the second episode of the new Brains Talking About Brains Jordana and Wilf are talking about the topic of how new cells that were grown in an adult (rat) brain were actually the cells that control the rest of the memory centres in the brain. Traditional thinking would say that new neurons are controlled and 'educated' by older neurons so these new neurons fit in with how the brain has worked in the past but this episode talks about how we can see very small populations of newly grown neurons running huge areas of the memory centres of the brain involving millions of neurons. At the end of the show, we also discuss what this means for human research since most human imaging techniques are not capable of studying such small groups of neurons in a lab.