Thin material structures come in a great variety: they range from fluid to solid, can be passive or active, within linear response or strongly nonlinear, relaxed or pre-stressed, etc. They display fascinating and often unexpected mechanical and rheological properties that influence the behaviour of living objects at length scales ranging from cell membranes to tissues and organs. The peculiar properties of these structures have a geometric origin and various continuous theories have been developed to model the underlying geometric interactions. However, independent of any particular model or material under consideration, there is still confusion about how structures that have long been well-understood in a fixed flat space translate to an evolving space. Already for static structures, classical bulk elasticity leads to a hierarchy of models for plates and shells. Considering their evolution provides additional possibilities. Furthermore, there is not only a larger variety of models, compared with bulk materials, also irregularities play an even more profound role. Topological defects for example have been postulated as key players in morphogenesis [1]. We here consider thin material structures with inhomogeneities; with internal degrees of freedom, with microstructures and defects; and with singularities. Prominent examples are the arrangements of cells in epithelial tissue, and how cell shape and neighbour relations influence bending properties [2], viscous active shell theories to model the actin cortex [3] or surface liquid crystal models from which coarse-grained models for asymmetric plasma membranes can be derived [4]. The main focus of the minisymposium is on modelling aspects addressing the interplay between the internal structures (cells, filaments, lipids, ...) and the geometric interactions determining the macroscopic shape evolution. We will bring together different disciplines: geometric partial differential equations, homogenization, numerical analysis, mechanics, biophysics and scientific computing and showcase the state of the art in mathematics of thin materials structures with applications in biology. We plan with 12 presentations.