Preface During our own work, or when we read other workers' articles in scientific journals, we invariably notice that there are “hot topics” related to plasma processes that are, on the one hand, very thought-provoking but which, on the other hand, can be rather contentious and the seeds of doubt. Some such topics were the centre of past discussions – think of plasma etching mechanisms in the early ‘80s, for example – but these were then either resolved or forgotten with passing time, because newer, more pressing issues caught the plasma community's attention. The identification and (hopefully) resolution of contentious topics in our field is something which important journals like Plasma Processes and Polymers (PPP) should not ignore; for this reason we decided to open a new procedure, starting with this issue, in part devoted to “debates”. We believe it is more productive to squarely face a problem, rather than to act like those famous three monkeys: one blind, one deaf and one dumb. This “debates” section aims to make PPP even more reactive and alive, and it will hopefully become a creative tool in the hands of our authors and readers, one that will drive forward the collective knowledge in our chosen area of research. PPP will solicit contributions that can constructively assist in resolving currently ongoing debates on various subjects in which unanimity is known not to exist among us. We plan to publish clusters of papers, communications, even letters-to-the Editor, in the same issue(s), so as to create a readily-accessible documentation of these “debates”. Grouping macroscopic data from different laboratories regarding the kinetics of plasma polymerisation; Mechanisms of plasma-based sterilisation and decontamination; Contact angle goniometry and wettability studies: methodologies and interpretations. The use of equation (1) in plots of Rm/F versus W/F allows one to identify different regimes in the plasma process. In particular, their latest article can help to understand the arguments that need to be addressed.1 The “spark” which persuaded us to open a debate on the dependence of deposition rate on the energy input – originally known as the Becker parameter,2 W/F, or since the late 1980s as the Yasuda parameter,3 W/FM – was ignited by a short paper submitted by Robert Short and David Steele, “Testing the Hypothesis: Comments on Plasma Polymerisation of Acrylic Acid”,4 (this issue) where they use expression (1), but suggest some controversies in its significance and application. Upon our request, the authors allowed us to reveal their manuscript to Dr. Hegemann, following which, both parties gladly agreed, with sporting enthusiasm, to open a constructive debate on the subject. In this context, Hegemann et al. then submitted a short reply-commentary, also published in this present issue.5 It is the firm intent of both the editors and the authors NOT to initiate a confrontation, but rather a CONSTRUCTIVE debate on how to resolve the contentious questions. This positive spirit clearly emerges from the letter jointly provided by the two groups of authors following this preface. The aim of this first debate is to understand the meaning of the various terms of Equation (1), to investigate the possibility of a more general treatment, and to identify and clarify the scientific basis of different plasma regimes by way of its use. In this current issue, devoted to the debate on “Views on macroscopic kinetics of plasma polymerisation”, you will find the letter co-signed by Hegemann, Short and Steele, along with their two papers. In order to further enhance the debate we have also asked several well-known experts in the area of plasma polymerisation to publish alongside with D. Hegemann and R. Short et al., and to provide some opening commentaries to the debate. Two of these commentaries are already included in this issue, and they express the experts’ views on the macroscopic kinetics of plasma polymerization.6, 7 Others are being planned in subsequent issues. We now invite our readers to also express their own opinions, provided that these are aimed at an improved understanding and that they do not discredit or insult anyone. Is it possible to compare results obtained using different plasma polymerisation reactors? Is it useful to implement the so-called “Becker parameter (W/F)” or Yasuda parameter (W/FM) in order to compare results from different laboratories? What is the exact meaning of the various terms in Equation (1)? Do plots based on Equation (1) allow one to define different plasma-physical regimes? What is the true meaning (if any) of the “activation energy” in Equation (1)? Is the term “polymerisation kinetics” a proper one in this context? We very much welcome your participation in this very exciting and promising “debate”.