I usually make to-do lists with timelines, and pen and paper does the trick for me.

This sounds strange to many people, but I work out for exactly 16 minutes every day, and do so at maximum speed by running 2.5 miles. This keeps me healthy without taking up too much time so I can stay focused on other things. It's one of the most efficient things I do each day.

The question that motivates my research is, if we can put a man on the Moon with 100,000 [people], what can we do with 100 million?

People are good at figuring out what's attractive, and computers are good at quickly searching and finding. You put them together, and bang!

It's hard to think of a time when I'm not working, but when that is the case, I like to travel and eat good food.

One fact we're particularly proud of is that there are more people learning languages on Duolingo in the US than there are people learning languages in the entire US public school system.

I worked on a number of projects that were used by millions of people and that also served as inspiration to what we now call crowd-sourcing.

Because education is such a broad area, I chose to focus on language learning.

If you get asked to do something that would take place down the road (say you get asked to speak at a conference that's a year away) and you wouldn't want to do it if it were taking place next week, then don't do it. This advice has helped me evaluate the opportunities that I truly want to dedicate my time to and those that I don't.

I am always able to keep a laser focus on one thing at a time without getting distracted. It helps that I try to break everything I do into small, achievable tasks.

I finished reading High Output Management by Andrew Grove, which had such valuable insights for leaders that I've been forcing managers at Duolingo to read the book.