From left to right: Image of Goya's paining, The Sacrifice to Vesta; the same painting with 50% THz visible; 100% THz view of the painting. mage courtesy Albert Redo-Sanchez/MIT Media Lab

Invisible to the eye and undetectable by most sensors, the small frequency of light called terahertz has eluded scientists for more than a century. That is finally changing — and revealing some amazing visuals in the process.