An overview of the soft X-ray polarimetry udertaken at BESSY over the last 10 years is presented.At BESSY,ten elliptical undulator beamlines are operating in the VUV and soft X-ray range.which enables the polarisation state of the synchrotron radiation to be changed from linear (horizontal or vertical)to left-or right-handed circular.It is essential that the degree of polarisation is known quantitatively,since this is a normalization quantity for many polarisation-sensitive experiments(e.g.MCD-spectroscopy).For a polarimetry experiment i.e.the measurement of the polarisation state of light,two optical elements are required acting as a phase retarder and a linear polariser,respectively.In the soft X-ray range,specially tailored multilayers(ML)operating in transmission and in reflection have been developed and optimized for this purpose.By matching the ML-parameters(period,thickness ratio)to an absorption edge of one of the constituent materials,a resonantly enhanced polarisation sensitivity can be achieved.Thus,ML-polarimetry is strongly connected with At-Wavelength Metrology of these polarisation optical elements,for which the instrumentation and results are presented.Examples of magneto-optical spectroscopy and polarimetry to determine properties of magnetic thin films or optically active substances are also presented(Faraday and Kerr effect,L-MOKE).