"The goal of the MARCHES project is to rationalise and optimize the interplay between electronically excited-states in complex molecular architectures. The simulation of the properties of large conjugated architectures is to be performed with ab initio tools explicitly taking into account environmental effects. Though efficient methods able to tackle such task are to be conceived during this project, we aim to enlighten coupled excited-states so to pave the way towards chemically-intuitive designs of new molecules. Indeed, the rationalisation and optimisation of the excited-state properties of large compounds is not only one of the major challenges of computational chemistry and physics, it also opens new horizons for emergent properties. In that framework, this project will allow to design molecular switches usable as building blocks for complex logic gates, subsequently unlocking crucial steps towards more efficient storage materials. To this end, compounds containing several photochromic switches coupled at the excited state have to be designed: this is an important challenge. Indeed, photochromes are actually limited to uncoupled or simply additive systems: emergent multi-addressable features are impossible to achieve."