Bill Gates on the toughest question he's ever had to answer

Bill Gates on Wednesday revealed that the toughest question that he has ever had to answer was not one related to his business.

Taking to Twitter, the co-founder of Microsoft shared that he was asked the question 25 years ago and has thought about it every day since: "Why do children die?"

"I think 'why do children die?' is one of the most important questions ever," Gates wrote in his blog. "It is hard to think of a measure of how a society is doing that reveals more than whether it is protecting its children, and especially its most vulnerable children. And the better we understand why children die, the more we can do to save them."

Bill Gates also acknowledged that child mortality is not an easy subject to talk about. "As a parent, I can’t imagine what it would be like to lose a child. It is shocking even to see the words “children” and “die” used in the same sentence," he wrote.

There is, however, a silver lining.