Cosmic inflation is the dominant paradigm to solve the aesthetic problems of the hot big bang cosmology and generate the seeds for structure formation. According to inflation, the universe underwent a brief period of extremely rapid expansion at very early times that resulted in a tiny patch to become very large in size and subsequently evolve to the observable part of our universe. In addition, the very rapid expansion converted quantum fluctuations into small inhomogeneities that grew due to gravitational clumping and gave rise to the structure in the universe.
To date, experiments confirm the simplest predictions from inflation. Ongoing experiments, such as PLANCK, will provide further observational evidence for inflation (primordial gravitational waves) and/or evidence for deviations from the simplest models of inflation (non-Gaussianity in the spectrum of the cosmic microwave background). However, the microscopic origin of inflation remains an important problem at the intersection of cosmology and particle physics. The challenge is to find a realistic model of particle physics that can also accommodate inflation without making ad-hoc assumptions.