From the time the first stars formed to the present-day, metals have witnessed the assembly of structure in the Universe in great detail. Although metals only form in stars and stellar remnants, they are ubiquitously present everywhere. However, we still do not understand how metals are effectively dispersed throughout the Universe, and the various

We will review both theoretical and obsevational aspects of gravitational wave backgrounds of cosmological origin. We will present a classifcation of backgrounds and a quantification of our ability to use them as a probe of early Universe phenomena, opening a new observational window to energy scales well above the reach of any terrestrial means

Very-high-energy (VHE >~100 GeV) gamma rays are absorbed in Earth's atmosphere and thus cannot be detected directly on Earth. Their fluxes are also typically too low to efficiently study them with satellite instruments. A VHE gamma ray entering the atmosphere initiates an electromagnetic cascade that induces faint flashes of blueish Cherenkov light