Reference charts are an important tool in modern primary medicine, covering many aspects of a person’s healthy development. There is, however, a big gap in their coverage: the human brain. If a doctor wants to know how well a child is growing, she can turn to clinically validated charts that lay out precisely how that child compares to the norm for their age and sex. Not only can the doctor look up, say, how many centimetres shorter or taller the child is than the average for their age, but exactly what height percentile they fall into. Can this help to avoid terminal illness?

