How do you think scientists were able to estimate the number of interneurons in the brain?

Hello,

I happen to be a neuroscientist and I'm not familiar with estimations of the number of interneurons in the brain.  First off all the neurons in the brain are essentially interneurons.  The term interneuron has been misused and abused for a long time.  The total number of neurons in the brain has been grossly over estimated so I think the whole thing is irrelevant at the moment.  This is about as absurd as the statement made a long time ago that we only use 10 percent of our brains (no way).  So how do you think scientists were able to estimate the number of interneurons in the brain?