What are terahertz waves?

What are terahertz waves
Terahertz waves are electromagnetic waves with frequencies ranging roughly from 100GHz and 10THz situated between millimeter waves and far-infrared radiation. Wavelengths range from approx. 0.03mm to 3mm.
Terahertz waves are safe as they can easily pass through materials, features a high degree of linearity, and unlike X-rays do not damage biological tissue.