There has been an exponential growth in the Chemical Sciences over the last two decades and in the current socio-economic environment it is apparent that the chemical sciences will be central in the drive for cleaner, more efficient energy sources and in solutions to issues of environmental pollution and global warming, while also underpinning advances in healthcare and supporting the drive to combat terrorism. Fundamental to all these issues is a deeper understanding of how processes occur at the molecular level and nanometre level, how this knowledge may be applied to generate materials with particular properties across all the size scales from molecules to bulk materials, and how these materials may find applications in modern society that will be of benefit to all. This is very much the Grand Challenge for the next few decades and incorporates not only chemical scientists, but also biologists, physicists, materials scientists, mathematicians, engineers, economists and educators. Much of the progress is dependant on an understanding of chemistry beyond the molecule and the directed assembly of extended structures with targeted properties . Our control over the assembly of atoms into molecules and materials, and the controlled assembly of molecules into both solid-state and aggregates in solution, remains very limited in scope, setting limits on the ability of chemists and materials scientists to design materials with desired properties even in cases where the underlying material requirements for a particular property are understood. Control of covalent bond formation in conventional synthesis of molecules with strong bonds is good and remarkably complex molecules can be prepared with confidence in multi-step (and increasingly in single-pot) syntheses. In contrast, much more limited control is possible in the preparation of solid-state materials, by techniques such vapour deposition for infinite structures, crystal engineering (employing non-covalent intermolecular interactions and utilising molecules as the basic building blocks) for molecular solids, or solution-phase assembly of molecular components using intermolecular interactions. Covalent bond formation in small molecules can be seen as the first step in an exploration of chemical assembly that needs to be dramatically extended if we are to meet our goal of achieving the a priori design of functional materials. Our contention is that this can be achieved by the incorporation of the use of molecular synthons and non-covalent interactions, to drive the assembly of more complex systems with the same degree of certainty and control that is already achievable for molecular synthesis. By achieving this goal, biological levels of complexity and function could be imposed on artificial materials, with all the evident benefits.We now propose to set up a network to identify the key areas of the Grand Challenge to develop methods to direct the assembly of extended structures with targeted properties and to produce a strategic roadmap to meet the challenge and overcome the barriers. The network will consist of a wide range of scientists, members of the industrial community, members of learned societies, funding bodies and policy makers. A series of general and themed meetings will be held and a roadshow will promote the Grand Challenge to the wider community. The propsal has been submitted by a group of seven researchers, all of whom have contributed extensively to the development of the ideas emanating from an initial Grand Challenges Meeting in late 2008. The team is Professor Paul Raithby (PI, University of Bath), Dr Harris Makatsoris (Brunel University), Professor George Jackson (Imperial College, London), Professor Matthew Rosseinsky (University of Liverpool), Professor Michael Ward (University of Sheffield) and Professor Chick Wilson (University of Glasgow).