The Galaxy's disk contains bright, hot, blue and white stars, accompanied by exquisite gas clouds fluorescing in red. An example in a neighbouring galaxy is the Tarantula Nebula. These are signs of youth, stars no more than 100 million years old. Older regions of the disk contain stars up to 6 billion years old, but if you turn away from the Milky Way, towards the Galaxy's north and south poles, you are looking into the past. Those directions are where the oldest stars --- called Population II stars --- are found, in the "halo" of the Galaxy.