Nebulae are interstellar clouds of dust, hydrogen, and plasma. These colorful regions of space are often the first stage of a star's life cycle; yet some, such as planetary nebulae or supernova remnants mark the end of a star’s life cycle. Many have shapes resembling familiar objects and are named as such.  Nebulae are often divided into either emission or reflection nebulae. Emission nebulae contain mostly ionized hydrogen, sulfur, and oxygen. Reflection nebulae do not produce significant amounts of visible light by themselves but instead reflect light from hot young stars nearby. Other types of nebulae include planetary nebulae and supernova remnants.

CCD images of nebulae are often quite colorful as the different gases emit red, blue, teal and orange colors when excited by radiation and these colors are collected using filters.

For more on Nebulae go to: http://en.wikipedia.org/wiki/Nebulae