The last decades have witnessed a substantial degree of maturation in demography and its applications to ecology, evolution, and conservation biology. This maturation, we argue, has been largely catapulted by quantitative progress on classical demographic methods (individual-based models, life tables, survival analyses, matrix population models) and the emergence of new ones (e.g. integrated population models, integral projection models). In this session, each speaker, leader in the development and the use of demographic tools widely applicable across the Tree of Life, will provide a historical perspective regarding the origins, progress to date, and future directions of these tools and the wide range of questions they allow to tackle, as it pertains to its ecological and evolutionary applications. Each speaker will conclude by providing an outline of the top five challenges of those demographic tools, and suggestions as to how to overcome them.