Exploring the nature of the symbiotic stars with high resolution spectroscopy.

There are some fundamental aspects of the "symbiotic phenomenon" which are poorly understood. Modern technology now allows to observe faint stars with efficient very high resolution spectrographs, such as the SARG mounted at TNG, which will be crucial for our understanding of the nature and evolutionary stage of symbiotic stars and related sytems. Of great importance will be the determination of luminosity, rotation, mass loss, chemical composition of the cool stellar components which is basic for settling the mass transfer in the system and tracing back its past history. High resolution observations are also needed to derive the velocity, temperature and abundance gradients in the nebula, and to unveil peculiar excitation processes.