The Dharavi area of Mumbai, India is home to nearly a million people, and one of the world’s largest slums. It was the setting for the movie Slumdog Millionaire, and many who live there are destitute and illiterate.

But in 2014, documentary filmmaker Nawneet Ranjan started a nonprofit called Dharavi Diary, which teaches children – mainly girls—English, math, computer applications like MS Powerpoint and Excel, and basic coding.

The article and video below show how girls have built mobile apps to tackle problems like sexual harassment, water scarcity, and lack of education.

Read the full story: Quartz India
Photo credit: Video screen shot