These massive clouds of interstellar dust and gas call the Eagle Nebula home. The pillars were composed of cool molecular hydrogen and dust that were being eroded away by photoevaporation from the ultraviolet light of relatively close and hot stars. The leftmost pillar was about four light years in length. The finger-like protrusions at the top of the clouds were larger than our solar system, and were made visible by the shadows of Evaporating Gaseous Globules (EGGs), which shielded the gas behind them from intense UV flux. EGGs are themselves incubators of new stars.
Parts of the clouds, particularly the finger-like projections you can see at various points along the pillars, are dense enough to collapse under their own weight, forming young stars. These embryonic stars continue growing as long as they can draw mass from the surrounding clouds.
Unfortunately the pillars were destroyed about 6000 years ago by a nearby supernova's shock wave; due to the time it takes for light to travel from the Eagle Nebula to Earth this won't be visible for another 1000 years.