The proposed research will form a comprehensive study of the chemistry and structure of evolved stars on the Asymptotic Giant Branch (AGB) and their circumstellar envelopes (CSEs), and form a powerful basis also to study the origin and evolution of heavy elements in galaxies, and the effect of AGB evolution on the formation of stars and planets. The focus of the proposed research is on the chemical properties of AGB stars and their CSEs, and on the structure and dynamics of the mass loss that creates the CSE. The project builds on the knowledge I have on AGB stars, and makes use of the observational and modelling tools I helped develop in the past years. I will describe the chemical complexity of AGB CSEs through the analysis of existing and future data, in observations with both a broad frequency range and high-spatial resolution. I will be able to identify the typical chemical reaction paths in the CSE and set constraints on the chemical processes. I will further observe the 3-dimensional structure of AGB CSEs and detached shells, and for the first time observationally describe the process that leads to the chemical evolution of AGB stars. The analysis of the data will be done using 1D and 3D radiative transfer models and 3D hydrodynamical models. The proposed project fully explores the capabilities of the Atacama Large Millimetre Array in Chile, and the recently extended bandwidth of the EMIR receiver on the IRAM 30m telescope in Granada, Spain - two observing facilities with a large investment from Europe. The research will be carried out at Onsala Space Observatory in Sweden, an institute with a long history in radio astronomy, and significant experience in scientific areas directly related to the proposed research. Working in Onsala I will strengthen existing and acquire new necessary technical, scientific, and personal skills in order to build a successful future career in astronomy.