Abstract:  We present new spectroscopic and photometric observations for a large sample of edge-on superthin galaxies. A galaxy is defined as superthin if the radial-to-vertical scale ratio of its stellar disk exceeds 9. The extremely "flat" stellar disks might require special conditions during their creation and evolution, which allows us to study the evolution of low density and low surface brightness galaxies. Our optical spectroscopy was performed with the  R~5000 spectrograph on the 3.5m telescope at the Apache Point Observatory (APO, New Mexico, USA) for more than 80 superthin galaxies. Most of them were also observed with the Near-Infrared (NIR) imagers in the H and K on the 3.5m telescope at APO and on the 2.5m telescope at MSU Caucasus Mountain Observatory. The stellar disk structural parameters and the ionized gas rotation curves derived from the observational data are a basis of our constrained rotation curve modeling that enables us to reliably estimate parameters of the dark halos in superthin galaxies. We discuss the properties of dark halos and dynamical features  of stellar disks that make the superthin galaxies unique.