Question: how many brain cells do we have?

Robert Lees answered on 10 Nov 2015:

Estimates say that we could have up to 100 billion brain cells – these cells are not all the same type though, some are neurons, which do all of the signalling (sending messages between cells) and some are glia, which support the neurons while they signal to each other.

You lose brain cells as you age and some diseases accelerate this process, called neurodegenerative diseases (what a mouthful to say, I still struggle…)