Colloids, i.e. systems comprised of particles of mesoscopic size suspended in a liquid, have been attracting increasingly more attention from scientists and engineers alike. This is partly due to the fact that nowadays colloids are present in many industrial products such as paints, oil additives, e-paper, and drugs. Apart from being a prominent segment of soft condensed matter, colloids also serve as versatile model systems for phenomena and structures known from solid-state physics, surface science, and statistical mechanics. Due to their large lengthscales and slow timescales they can be readily studied using tabletop experiments, providing insight into processes which are not easily accessible in atomic systems.

Organized within the Marie-Curie Initial Training Network COMPLOIDS, the School was conceived to present the diversity of research in the area of colloidal systems in a comprehensive style to young scientists and to indicate novel trends in the field. Colloidal science is distinguished by an intimate connection between experiments and theory, and the School addressed experimental, theoretical, numerical results and methods. The topics of the lectures covered a broad spectrum of aspects starting from the synthesis of colloids and their use in commercial products. Particular attention was paid to the different types of colloidal interactions, how they can be measured and how they lead to ordered and disordered structures. Colloidal systems do not only allow us to address equilibrium states but also provide appealing options to investigate non-equilibrium phenomena, some of which were discussed in lectures on active Brownian motion and on stochastic thermodynamics.

The School was designed as a series of minicourses, most of which consisted of five or three lectures. The minicourses were complemented by seminars addressing selected recent advances in the field and by poster presentation of the participants. We did our best to accept as many participants as possible, giving priority to Ph.D. students. The complete list of participants is included in this volume.

The School took place at the magnificent location of the Villa Monastero in Varenna, which stimulated an intense scientific exchange between the lecturers, the students, and the directors. The local organizer, Barbara Alzani, together with Ramona Brigatti and Marta Pigazzini, did a truly remarkable job in making this meeting memorable and unique. Their mindfulness and readiness in organizational issues were instrumental for the overall success of the School. Also essential for the organization was the assistance of Roberta Comastri (administrative office), Monica Bonetti (editorial office) and Marcella Missiroli (production office). Finally, we thank the Italian Physical Society (SIF) for making this event possible. In these proceedings, the authors review the state of the art of colloidal science in a pedagogical way, discussing both the basics and the latest results. We hope that the volume will serve as a reference both for students entering this rapidly growing field and for the experts.

C. Bechinger, F. Sciortino and P. Ziherl