With the rapid emergence of digital devices, an unstoppable, invisible force is changing human lives in ways from the microscopic to the gargantuan: Big Data, a word that was barely used a few years ago but now governs the day for many of us from the moment we awaken to the extinguishing of the final late-evening light bulb. This massive gathering and analyzing of data in real time is allowing us to not only address some of humanity biggest challenges but is also helping create a new kind of planetary nervous system. Yet as Edward Snowden and the release of the Prism documents have shown, the accessibility of all these data comes at a steep price. The Human Face of Big Data captures the promise and peril of this extraordinary knowledge revolution.