(non)Gaussian lensing of a (non)Gaussian cosmic microwave background

Weak gravitational lensing changes temperature and polarisation correlations of the cosmic microwave background and has been detected by the Planck-mission at high statistical significance. It offers a unique look at the cosmic large-scale structure at high redshifts beyond three. Common assumptions are that of a Gaussian microwave background with Gaussian statistics of the fluctuations, both of which are known not to be true. I introduce in my talk CMB-lensing an a possible perturbative and non-perturbative solution to lensing a non-Gaussian CMB with non-Gaussian structures.