Microsoft co-founder and philanthropist Bill Gates offered new college graduates some valuable advice this week in 14 simple tweets. The tech titan and richest man in the world, who dropped out of Harvard in 1975, took to Twitter on Monday to share his top tips for new graduates, lessons he wished he had learned before leaving college, and some of his biggest regrets.

"New college graduates often ask me for career advice," he wrote in a series of tweets, starting off with a reference to the classic movie "The Graduate".

"AI, energy and biosciences are promising fields where you can make a huge impact," Gates wrote. "It's what I would do if starting out today. Looking back on when I left college, there are some things I wish I had known."

Intelligence, for instance, is "not one-dimensional" and takes many different forms. He also noted that it is "not as important as I used to think".

Gates also delved into some of his biggest regrets after dropping out of college.

"When I left school, I knew little about the world's worst worst inequities. Took me decades to learn," he said. "You know more than I did when I was your age. You can start fighting inequity, whether down the street or around the world, sooner."

The billionaire also discussed the importance of choosing both personal and professional relationships wisely.

In a longer Mic article, Gates said: "I encourage you to surround yourself with people who challenge you, teach you and push you to be your best self. Melinda does that for me, and I am a better person for it. Like our good friend Warren Buffett, I measure my happiness by whether people close to me are happy and love me, and by the different I make in other people's lives."

If there was one graduation present he could give any new graduate, Gates said it would be a copy of "The Better Angels of Our Nature" by Steven Pinker.

Describing it as the "most inspiring book I've ever read", Gates said the renowned Harvard psychology professor "shows how the world is getting better".

Expectedly, the tech giant's recommendation has propelled Better Angels' sales on Amazon by over 607,000%.

Gates also discussed the nature of living in 2017 saying it is "the most peaceful time in human history."

"Sounds crazy, but it's true. This is the most peaceful time in human history," he wrote. "That matters because if you think the world is getting better, you want to spread the progress to more people and places."