Gravity. The stars in day. Thoughts. The human genome. Time. Atoms. So much of what really matters in the world is impossible to see. A stunning animation of John Lloyd's classic TEDTalk from 2009, which will make you question what you actually know.
This lesson was adapted from a TEDTalk given by John Lloyd at TEDGlobal 2009: http://www.ted.com/talks/john_lloyd_inventories_the_invisible.html
John Lloyd mentions several things that are too small to see. He says atoms are too small and that we will probably never have the ability to see them. Just how small are they? http://ed.ted.com/lessons/just-how-small-is-an-atom
Furthermore, Lloyd mentions our ability to see the stars and the planets and our inability to see what holds them apart. http://ed.ted.com/lessons/jon-bergmann-how-to-think-about-gravity
In 2010, scientists were able to watch (for the first time) electrons moving in real time. We think about electrons as invisible bits of existence, but with incredible advances in technology, we're able to see more and more of the world that we never thought we would. http://www.popsci.com/science/article/2010-08/first-time-scientists-watch-electrons-dance
Invisibility finds its way into movies, science fiction novels, comic books, and more. It draws multitudes of people to shows in some of the largest venues in the world (David Copperfiled or Sigfriend and Roy, for instance). However, there is a scientific side to what may appear to be all smoke and mirrors. There are also plenty of instances where invisibility may be due to the laws of physics. See how invisibility can be observed in the world without having to purchase a ticket to a show in Las Vegas: http://en.wikipedia.org/wiki/Invisibility
Just a few generations ago, it was never imagined that we would have the ability to work with "invisible" matter. However, nanotechnology is a burgeoning field of science that will one day affect nearly every part of our lives. http://videos.howstuffworks.com/howstuffworks/462-how-nanotechnology-works-video.htm