Editor: Prof. Cosimo Bambi is currently Xie Xide Junior Chair Professor at the Department of Physics of Fudan University, in Shanghai. He received the PhD from Ferrara University (Italy) in 2007. He was a postdoc at Wayne State University (Michigan), at IPMU at The University of Tokyo (Japan), at LMU Munich (Germany). He has published about 90 research papers and has more than 2,000 citations. His H-index is 29. Chapter authors:  Jean-Pierre LASOTA – HIRSZOWICZ is Directeur de Recherche Emerite; Institut d'Astrophysique de Paris. He has 240 scientific publications and 7170 citations by Jan. 2014.  Tomaso Belloni is "Primo Ricercatore" at INAF Osservatorio Astronomico di Brera since 1999. He published 566 articles (262 on refereed journals) with 10,606 citations. His H-index is 47. He is referee of all major international astronomical journals.  Matthew Middleton is currently Ernest Rutherford STFC Fellow at the IoA, University ofCambridge. He has published 45 articles with H-index of 17.  Feng Yuan is a professor and the director of Research Center for Galaxy and Cosmology,  Shanghai Astronomical Observatory. He has published more than 60 journal articles, and the total citations are more than 2000.    Daniele Malafarina is currently assistant professor at the School of Science and Technology of Nazarbayev University, Astana (Kazakhstan). He has published over 30 articles, including an invited review article.