Gamma rays and neutrinos are two complementary messengers that help us to
understand the physics processes that shape the high-energy universe.
They also might allow us to identify the particle nature of dark matter.
I will introduce the most sensitive telescopes in their respective energy
ranges to study astrophysical neutrinos and gamma rays, the IceCube
telescope located at South Pole and the satellite-based Fermi Large Area
Then I will focus on the lessons we can learn from observations of the
of gamma rays and neutrinos that is emitted from all the gamma-ray and
sources throughout the universe that are too weak to be detected