Why do teenagers suddenly and unexpectedly become irrational, uncommunicative and emotional? Your child is changing, trying to figure themselves out.Their brain and bodies are undergoing extensive reorganisation. Inexplicable habits - unprompted emotional outbursts, risky irrational behaviour, addiction to social media, inability to get up in the morning - are not their fault. In large part, they are due to their undeveloped and disconnected brain, which is neither an adult nor a child brain. I discuss the huge changes that happen to teenage brains during adolescence and how these explain many of their habits and behaviours.