By Robert Harrison for Quartz.

Philanthropy isn’t what it was 50 years ago. In fact, the sector isn’t even what it was last year. From the emergence of Silicon Valley philanthropy, to the growing influence of millennials as social entrepreneurs, to new adventures in virtual reality — 2015 took philanthropy on a ride that captured headlines and our imagination.

But this new world of philanthropy wasn’t built overnight. Ever since the Clinton Global Initiative was founded as an experiment in 2005, we have seen firsthand how bringing together the world’s top business, government, and civil society leaders could help address the great challenges of the 21st century. A decade—and by our count, more than 430 million improved lives—later, CGI members are helping shape modern philanthropy. Here are some of the lessons we took to heart in 2015:

1. Work together across sectors

Whether partnering to transform parental leave in corporate America or to improve the livelihoods of over 300,000 smallholder farmers, some of the world’s most influential organizations spent 2015 making an even bigger impact by working with others.