For decades, if we wanted to see inside the brain, we had to inject air into the patient's spinal column. 

It was painful. It was described as torture. 

Then in 1971, a British engineer changed everything when he performed the first CT scan.

 And for the first time, we could see what was happening inside the brain. 

It was painless, convenient, and an absolute game-changer. 

But just because we could now see inside a person's brain, doesn't mean we know what it's thinking.