[en] This year is the 10th anniversary of the discovery of the first high-transition temperature (T_c) superconducting compounds. Since then, these materials have taught us much new physics. Few issues have been s hotly debated as the controversy about flux lattice melting. Two recent papers by Kes and co-workers at the University of Leiden drive right to the heart of this issue. The superconducting state, in general, does not like magnetic fields. To avoid the presence of a magnetic field in its interior, a superconductor responds in interesting ways. There are two important critical fields for a superconductor that define its response. The first is the lower critical field H_cl; for fields less than this value, superconductors expel the applied field (the Meissner effect). The second is the upper critical field H_c2; for fields above this value, superconductivity is destroyed. The high-T_c superconductors are examples of what are called open-quotes strongly type IIclose quotes materials, those for which H_c2>>H_cl. All of the technologically important superconductors are of this type, and so their study is essential if applications are to be realized. This article goes on to discuss the research, background, and future of these. 4 refs., 1 fig