This picture was taken by Soichi Noguchi looking out of the newly installed ISS cupola, which provides dramatic vistas of space from inside the station. You can see the Soyuz module that carried astronaut Tracy Caldwell Dyson on board-- incidentally, with Discovery on its way to the ISS carrying three women, this will be the first time four women will have been in space simultaneously.
[Update: According to commenter Ben Honey, that's actually a Progress capsule, and not the Soyuz. The profile does match a Progress, so I assume he's right. I stand corrected.]
This image is simply fantastic. The aurora, commonly called the northern lights, are caused by subatomic particles slamming into our atmosphere and ionizing the oxygen and nitrogen atoms there like shrapnel from bullets hitting a target. Guided by the Earth's magnetic field, these particles tend to hit at high latitudes. The glow itself is similar to that of a neon sign: when the wayward electrons recombine with the atoms, they give off light. The colors are characteristic of the atom in question, and can be used to identify the atmospheric constituents. The green glow is actually much lower than the ISS; that part of the aurora is usually at a height of 100 or so kilometers (60 miles), while ISS is at 400 km (240 miles). The red glow can reach higher, to more than 500 km (300 miles), so when Soichi says he is flying through the aurora he is literally correct. The fantastic speed of the ISS is apparent in the trailing of the stars in the image, and the streaking of the purple clouds below. Astonishing, lovely, poetic, beautiful... and Holy Haleakala, real. When we humans want and choose to, we can fly through the northern lights. What else can we accomplish when we set our minds to it?