EPJ - Special Topics (EPJ ST) publishes topical issues which are collections of review-type articles or extensive, detailed progress reports. Each issue is focused on a specific subject matter of topical interest. The journal scope covers the whole spectrum of pure and applied physics, including related subjects such as Materials Science, Physical Biology, Physical Chemistry, and Complex Systems with particular emphasis on interdisciplinary topics in physics and related fields. Only proposals for a complete issue will be considered. Proposals will be refereed and should be submitted to either Anne Ruimy, EDP Sciences, anne.ruimy@edpsciences.org or Sabine Lehr, Springer, sabine.lehr@springer.com Discussion and Debate Issues The journal offers a new feature in form of Discussion and Debate issues. The aim of such topical issues is the balanced critical presentation of specific unsolved problems, controversial topics, rival theories, alternative methodologies, and negative results of interest at the cutting edge of scientific and technological development.