Mapping the Large Scale Structure of the Universe
  In a large scale view of the universe, galaxies are the basic unit of structure. A typical bright galaxy may contain 100 billion stars and span tens of thousands of light years, but the empty expanses between the galaxies are much larger still. Galaxies are not randomly distributed in space, but instead reside in groups and clusters, which are themselves arranged in an intricate lattice of filaments and walls, threaded by tunnels and pocked with bubbles. Two ambitious new surveys, the Two-Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS), have mapped the three-dimensional distribution of galaxies over an unprecedented range of scales. Astronomers are using these maps to learn about conditions in the early universe, the matter and energy contents of the cosmos, and the physics of galaxy formation. 
David H. Weinberg