The James Webb Space Telescope (JWST) is meant to be the successor to the Hubble Space Telescope, which has peered further into the universe than any other scientific instrument to date and brought us hundreds of breathtaking pictures such as the Hubble Ultra Deep Field (HUDF) shown to the right. At several different times I have used the HUDF as a desktop wallpaper because I find it so inspiring. Every speck on that image is an entire galaxy, consisting of up to hundreds of trillions of stars each. It is also the furthest back in time that we have ever seen. The image shows what this tiny portion of the universe (roughly one thirteen-millionth of the total area of the sky) looked like approximately 13 billion years ago. It is an amazing glimpse of the magnitude of the universe that we inhabit, and I firmly believe that the Hubble is one of the greatest achievements of mankind in my lifetime.
The JWST is an even more powerful space telescope with a planned launch in 2018. It will be able to see even further and earlier than the Hubble. From NASA:
Webb will find the first galaxies that formed in the early Universe, connecting the Big Bang to our own Milky Way Galaxy. Webb will peer through dusty clouds to see stars forming planetary systems, connecting the Milky Way to our own Solar System.