This book contains eight chapters. The first three focus on three different layered systems, namely, mercurocuprate, BSCCO and RE-123 and present exciting features like their unusual chemistry, vortex physics and novel characteristics of the multilayers formed with some of them. The remaining five chapters of the volume describe studies carried out on recently discovered magnesium diboride, which superconducts at 39K. New and interesting work has been presented which describes, noteworthy advances in their flux pinning and mechanical properties and also bring out their future potential as this films and SQUID devices.