Question: how many brain cells are in the brain ?

Mariana Vargas answered on 21 Mar 2010:

Hello there! Great question. There is no absolute answer for this, only estimates using histological techniques (that is looking at brain sections on the microscope and extrapolating the number of counted neurons in a small sample to a higher volume). It is estimated that a human brain contains of about 85 billion neurons (85 000 000 000). But the most exciting thing about this is… because neurons make hundreds of connections with each other (about 1000 connections each)… then the number of actual connections is close to 100 trillion! (100 000 000 000 000).