On the very largest scale, on a size that is unimaginable to the human mind, the universe is structured into a continuous network of interlaced superclusters of galaxies. Long strings of galaxies cross vast expanses of open voids of space, held together by invisible forces of gravity. The long strands of galaxies merge together in giant nodes of galaxy clusters that contain hundreds or thousands of galaxies. These networks go on and on across the universe, bridging the voids between huge collections of galaxies. This structure containing long strands of galaxies, merging at huge intersections of galaxy clusters, surrounded by large voids of space with few galaxies, creates a vast network that resembles a sponge the size of the universe.
Understanding the size and age of the universe requires us to abandon our common understandings of space and time, and explore the truths that the universe reveals to us. Microwave surveys of the night sky have helped us understand that the universe is 13.8 billion years old. These measurements support the theory that the universe was created from a single point in space in an event now known as The Big Bang. Since that time, space has continued to expand in all directions. New techniques for accurately measuring distances in the deep universe indicate that the rate of expansion of the universe is actually increasing, as all points in space accelerate away from all other points. As odd as it sounds, the current best measurement of the size of the known universe is 96 billion light years across. How is this possible in a universe that is only 13.8 billion years old? The links below help to explain this mind-bending observation.
For more information:
Observable Universe - Wikipedia