Dear Kevin

Asking a doctor how many cells are in a human body is like asking an architect how much her buildings weigh.

How many cells?

I've no idea. Billions? Trillions?

It's either 10⁶ or 10⁹ cells in a cubic cm of breast tumour. You get a mutation every 10⁶ breast cancer cells.

Figure it out yourself, Kevin. How many cubic centimetres are in you?

Clue: Who said, 'Eureka!' and why?

Yours sincerely

BTW I think there are about a trillion neurons (nerve cells) in a human brain.