Iron-based superconductivity，then and now

High temperature superconductivity is one of the unresolved problems at the cutting edge of condensed matter physics, stimulated greatly by the recent discovery and studies of iron-based superconductors. Here we briefly review the history and basic concepts of superconductivity,and the status of current research on copper-oxide high temperature superconductors. We will explain why iron-based superconductivity is so important as a key bridge between conventional and high temperature superconductivity, and remark, in particular, on the significant contributions from China.