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

I present the recent results obtained using the updated version of MG-MAMPOSSt, a code that constrains modified gravity (MG) models viable at cosmological scales using determination of galaxy cluster mass profiles with kinematics and lensing analyses. I will discuss limitations and future developments of this method in view of upcoming imaging and

I will review the status of the QUIJOTE (Q-U-I JOint TEnerife) experiment, a project led from the IAC with the aim of characterising the polarisation of the Cosmic Microwave Background (CMB) and other galactic or extragalactic physical processes that emit in microwaves in the frequency range 10-42GHz, and at large angular scales (1 degree