The Eagle Nebula is an immense structure of pillars of gas and dust located some 7000 lightyears away toward the constellation Serpens.
It's a so-called "open cluster"; a site of new star formation. The pillars, several lightyears long,
are concentrations of dense molecular gas, which are able to withstand the effects of the intense ultraviolet light emitted by newly-formed hot, massive stars, located above the nebula.
The knots and filaments on the surfaces of the pillars are formed as the surface of the pillars — heated by the hot stars — boils away.
I have observed the Eagle Nebula several times (because it's so beautiful) with different filters.