How glass, tin, and mercury converged on a Venetian island in the 15th century to fundamentally change the way we look at ourselves.

From the article, about Steven Johnson’s book, How We Got to Now: Six Innovations That Made the Modern World :

“…..the role of glass in the journey of our self-image extends beyond the technology and into how we think about the human countenance itself….

At the exact moment that the glass lens was allowing us to extend our vision to the stars or microscopic cells, glass mirrors were allowing us to see ourselves for the first time. It set in motion a reorientation of society that was more subtle, but no less transformative, than the reorientation of our place in the universe that the telescope engendered……

The mirror played a direct role in allowing artists to paint themselves and invent perspective as a formal device; and shortly thereafter a fundamental shift occurred in the consciousness of Europeans that oriented them around the self in a new way, a shift that would ripple across the world (and that is still rippling)………..”

Read more :

http://www.brainpickings.org/2014/11/12/steven-johnson-mirror-selfie/