Dark energy fractal illustration. Scientists can only account for about 30 percent of the matter they think is present in the universe, a combination of ordinary matter and so-called dark matter. This leaves 70 percent unaccounted for and is thought to be made up of a mysterious substance called dark energy, an energy field rather than subatomic particles. Observations of supernovae show them to be accelerating away from each other and it is thought that dark energy may be responsible for this inflation. Cosmic inflation is the exponential expansion of space in the early universe. The inflationary hypothesis was developed in the 1980s by physicists Alan Guth and Andrei Linde. It explains the origin of the large-scale structure of the cosmos. Quantum fluctuations in the microscopic inflationary region, magnified to cosmic size, become the seeds for the growth of structure in the Universe