SPS Focus is a new publication series of the Swiss Physical Society where a single topic is presented and placed in focus for a broader audience, hence its name. The series will be published irregularly and is aiming at topics that can provoke broad interest. Research highlights causing a paradigm change like e.g. quantum computing would be among those topics destined for a SPS Focus, but also interactions of physics with other disciplines are of high interest. Interdisciplinary focus topics, like in life sciences, often need to work out physical facts and apply tools developed from physics to reliably model, predict or even control complicated organisms from the micro- to the macro scale. Therefore, the presentation style of any SPS Focus is intended to appeal not only to physicists, but to scientists in general and including the interested public. To achieve this goal, renowned experts are invited to describe the state of art of a specific topic in an accessible way for the non-expert.