Dark Matter is one of the mysteries in modern physics. While different astronomical and cosmological observations suggest that there is approximately 5 times more invisible than (electromagnetically) visible matter, its existence can only indirectly be interfered from its various gravitational effects. Examples are the flattening of galaxy rotation curves, the strength of gravitational lensing or the structure of the cosmic microwave background. The latest results of the Planck satellite indicate that the Universe contains 4.9% ordinary matter, 26.8% Dark Matter and 68.3% Dark Energy.
At the present time, there is no direct (non-gravitational) prove for the existence of any form of Dark Matter, but in particle physics many theoretical extensions to the standard model exist that predict viable Dark Matter candidates. However, the experimental observations do not favor any specific new physics approach.