Abstract: One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the Cosmic Microwave Background. These originate from tensor fluctuations of the metric produced during the inflationary phase. Their detection would therefore constitute a major step towards understanding the primordial Universe. The expected level of these anisotropies is however so small that it requires a new generation of instruments with high sensitivity and extremely good control of systematic effects.