2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/183665Narrow-line Seyfert 1 galaxies are identified by their uniform optical spectral properties. Studies of samples of NLS1s reveal, however, a range of X-ray spectral and variability behavior, and UV spectral behavior. We describe the range of behavior observed, illustrating with a comparison of the XMM-Newton and HST data from the NLS1s 1H0707-495 and TonS180, and discuss how the spectral energy distribution may causally link the UV and X-ray properties.8 pages, 6 figures, 1 color figure, invited contribution for the conference "Stellar-mass, Intermediate-mass, and Supermassive Black Holes", held in Kyoto, Japan, October 28-31, 2003, to be published in Progress of Theoretical Physics SupplementAstrophysicstext