The human brain weighs about three pounds [1.4 kg] and is roughly the size of a grapefruit, yet it contains some 100 billion neurons, or nerve cells, all of which form an incredibly complex network.
Inimese aju on umbes 1,4 kilogrammi raskune ning suure greibi mõõtu, ent selles on umbes 100 miljardit neuronit ehk närvirakku, mis moodustavad uskumatult keeruka võrgustiku.