Many different polarimetric instruments have been and are being constructed throughout Europe, and they have as many different science goals. There is therefore a wide range of expertise on polarimetric techniques and technology, which is not yet being fully exploited. Future instrument developments will certainly benefit from exchanging the various ideas on how to measure a specific polarization signal. This Working Group for the first time brings together instrumentalists and industrial partners, and stimulates cross-fertizilation between them. It constitutes a think-tank for novel polarimetric methods that is also available to the other Working Groups when they come up with ideas for new polarimetric science.