Chemical modelling covers a wide range of disciplines, and this book is the first stop for any chemist, materials scientist, biochemist, or molecular physicist wishing to acquaint themselves with major developments in the applications and theory of chemical modelling. Containing both comprehensive and critical reviews, it is a convenient reference to the current literature. Coverage includes, but is not limited to, considerations towards rigorous foundations for the natural-orbital representation of molecular electronic transitions, quantum and classical embedding schemes for optical properties, machine learning for excited states, ultrafast and wave function-based electron dynamics, and attosecond chemistry.