Foreword.- Alexander Berglund and Robin Stoll: Higher structures in rational homotopy theory.- Ricardo Campos and Albin Grataloup: Operadic deformation theory.- Coline Emprin and Geoffroy Horel: Weight structures and formality.- Damien Calaque and Victor Roca I Lucio: Associators from an operadic point of view.- Olivia Borghi and Marcy Robertson: Lecture notes on modular infinity operads and grothendieck-teichmüller theory.

This book presents the notes originating from five series of lectures given at the CRM Barcelona in 21-25 June, 2021, during the “Higher homotopical structures” programme.

Since their introduction 60 years ago, the notions of infinity algebras (Stasheff, Sugawara), higher categories (Boardman-Vogt), operads (May), and model categories (Quillen) have given rise to powerful new tools which made possible the resolution of open problems and prompted revolutions in many domains like algebraic topology (rational homotopy theory, faithful algebraic invariants of the homotopy type of spaces), deformation theory (formality theorems, formal moduli problems), and mathematical physics (quantization of Poisson manifolds, quantum field theories), to name but a few. 

This theory of higher structures using operadic calculus is currently under rapid development. The aim of this book is to provide the community with an accessible state-of-the-art, while at the same time giving interested researchers and advanced students a brief overview on the subject.