Safecast is a non-profit organization and a global network dedicated to the effort of collecting and sharing radiation measurements. Immediately after the March 2011 disaster in Japan, a group of concerned citizens, who became the founders of Safecast, gathered in their desperate need for accurate information about radiation levels in Fukushima and other areas affected by the Dai-ichi nuclear meltdowns. Safecast developed a reliable Geiger counter that records radiation levels every 5 seconds and instantly posts the data on the Internet. The device’s open-source technology is made available free of charge to anyone who is interested. The endeavor is an exemplary model of citizen science making a positive contribution to society.