Symbiotic stars, which are interacting binary stars usually composed by a late type giant and a very hot/luminous white dwarf, are a powerful laboratory to investigate mass loss phenomenon relevant to a wide range of astrophysical topics: aspherical mass loss, collimated winds from accretion disks, colliding winds, mass loss induced by violent thermonuclear outbursts and its interaction with old circumstellar wind-remnants and the interstellar medium. In recent years, we have discovered optical emission nebulae around 8 symbiotic stars, which represent a large fraction of the complete sample known to date. These extended (0.02 to 2~pc) nebulae are the key to reconstruct the mass loss history from these systems in the last <2000 years. The observation of (multiple) bipolar nebulae, elliptical and ring-like objects, knotty collimated ejecta, and bended jets indicates that a wide variety of dynamical processes has to be considered in order to fully account for the morphological and kinematical properties of the nebulae. We present here a detailed kinematical study, at high spectral (R=40000) and spatial (<=0.5 arcsec) resolutions, of the ring nebula around He 2--147 and of the complex ejecta of HM Sge.