The top image has been processed to display the faint regions that surround the Eagle Nebula. The bottom image has been processed to bring out the detail in the "Pillars of Creation" at the centre of the image. The bottom photo is at 100% scale.
The gas cloud is gradually being eroded by the ultra violet light from the hot massive new born stars within the nebula. The densest clouds, made up of dust and molecular hydrogen survive longer than their surroundings. This erosion has formed the "Pillars of Creation". This is a region of active star birth.For more details, see http://seds.org/HST/M16Full.html