Foreword.- Jue Lin, Elissa S. Epel and Elizabeth H. Blackburn: Telomeres and telomerase in human health and disease.- Susumu Tonegawa and Thomas J. McHugh: Molecular and circuit mechanisms for hippocampal learning.- Jef D. Boeke, Wenfeng An, Lixin Dai, Edward S. Davis, Jeffrey S. Han, Kathryn A. O'Donnell, Lisa Z. Scheifele, Sarah J. Wheelan: Retrotransposons - natural and synthetic.- Roland Ivanyi-Nagy and Jean-Luc Darlix: Ancient retrotransposons as possible remnants of the primitive RNA world.- Kazazian HH, Jr., Seleme, MdC, Babushok DV, Ostertag DM, Vetter MR, Mandal PK.: Human diversity and L1 retrotransposon biology: creation of new genes and individual variation in retrotransposition potential.- Alysson R. Muotri, Maria C. N. Marchetto & Fred H. Gage: From the 'RNA World' to brain complexity: generation of diversity.- Robert H Yolken, Hakan Karlsson, Ioannis Bossis Linnea Aspl, Faith Dickerson, Christoffer Nellaker, Michael Elashoff , Elizabeth Rubalcaba, Raphael P. Viscidi: Endogenous retroviruses and human neuropsychiatric disorders.- Timothy J. Crow, JS Close, Heui-Soo Kim, MT Ross: Is psychosis due to retroviral/retrotransposon integration close to the cerebral dominance gene?.- Edward C. Gilmore, Christopher A. Walsh: Microcephalies and DNA repair.- Subject index.