Twenty-one of the world’s brightest young scientists gathered at Google’s headquarters in Mountain View today to celebrate their achievements and present their projects to a panel of renowned judges at the Google Science Fair finals.

Chosen from thousands of projects from more than 100 countries, these top 15 projects impressed the judges and public with their breadth of topics: from cancer research to vertical farming, 3D electronics to dementia. It was a tough decision, but we’re proud to name these three projects the winners of this year’s Google Science Fair: