Over the past decade there has been a significant expansion of activity in applying the techniques and theory of algebraic topology to real world problems. The expression `applied algebraic topology' is no longer an oxymoron! This expansion has generated new mathematical theory, new computational techniques, and even commercial startups. However, there is still an important component of this topological approach that has not been treated in any depth, and this is the inherently stochastic nature of the world. Consequently, there is an urgent need to complement recent developments, which have been primarily deterministic, with sophisticated stochastic modelling and analysis. The current proposal aims to attack this issue by applying algebraic topological thinking to random systems.Over the past two years, the PI Adler and colleagues have organised workshops in Banff, Palo Alto and Chicago with tens of researchers from topology, probability, statistics, random networks, image analysis and other areas, with the aim of defining the important problems that `random algebraic topology' should address. These brain trusts have born fruit in terms of setting some clearly defined goals, many of which help motivate the core of the current proposal, which is by far the most ambitious of a number of earlier and current projects.These endeavours are expected to have -- and are to a considerable part driven by -- applications to areas outside of mathematics, while at the same time having deep, intrinsic, mathematical interest. The multi-faceted aspect of the proposal, involving a number of areas within mathematics that do not usually appear together, is highly novel and requires the setting up of a large and coordinated team of researchers. This will include the PI, graduate students and postdoctoral fellows, and short and medium term visiting scholars from a variety of disciplines