It's almost as bad when someone shows up behind you, those beams shining directly into your rearview mirror. Yet in night mode any mirror objects save for the offending headlamps seem obscure and hard to see.
Electrochromic technology is a process of darkening glass by applying an electrical current.
Such a mirror contains a thin layer of electrochromic gel sandwiched between layers of glass. When sensors detect glaring light, they energize an electronic system that causes the gel to darken and absorb the light's brightness, thus paring the glare's intensity. Once the glare passes, the mirror reverts to normal mode of high reflectivity. Driver never has to lift a finger because the mirror changes automatically, much like photosensitive eyeglasses darken relative to light exposure. The Night Vision Safety Mirror, which dims automatically, also has a built-in digital electronic compass, a digital thermostat to display outside temperature, plus an ice indicator that pops on for one minute when the temperature dips below 37 degrees.