One of the most important current areas in chemistry is developing new materials that are able to respond rapidly and reliably to changes in local environment, and send out signals that let us know what is happening. These materials can be used as sensors in a wide range of situations and are used in many aspects of modern life, from press-on patches to take a patient's temperature to solid-state electronic components in modern televisions. The clever chemistry used to develop such materials can help make materials with just the right property for the right situation - they can be made tuneable. The chemist aims to produce new, smart, responsive materials to be manufactured into useful devices for real applications. To produce new, better, more energy efficient materials that can benefit UK manufacturing and keep the UK at the forefront of technological developments, we need to find new ways of controlling the properties and functions of molecules to produce even smarter materials. This proposal aims to do just this, using a new way of tuning the properties of materials. Most smart materials operate in an equilibrium state, while most complex systems, such as animals and humans, operate in non-equilibrium states that are much more responsive to small changes in environment and can thus function in more complex ways; indeed, if the human race operated in equilibrium, life would cease to exist as we know it! We need stimuli to keep us alive we wish to take inspiration from ourselves in developing a new generation of smart materials, by applying the ideas of states to the development and operation of new materials. These will operate in different ways giving access to new properties and functions. Our new approach to designing new materials that operate in non-equilibrium conditions, uses or excited states - this means that we stimulate the material, for example by a light pulse, and by doing so we change the way in which the chemical structure of that material delivers its properties. Effectively using excited states we can change the behaviour of the electrons and hence the effect of the chemistry of a material without apparently changing its chemistry at all! Many current switchable smart materials must include regions of a different chemical or physical composition - these defects are very important for giving a material its properties, but produce a heterogeneous material - a good example is the which physicists are developing. We will be able to introduce the same tuneable function but in chemically homogeneous materials, with real advantages for controlling their stability and performance. To achieve this, we have to make significant advances across a range of areas, including designing the chemistry of metastable switchable materials, generating excited states that give the desired change of property, controlling these and eventually to build these into useful devices for applications. Our proposal will allow us to develop ways of controlling the properties and functions of these metastable materials in ways that are not possible currently. There are many possible applications for these new materials including more efficient conductors and more miniaturisation of devices that rely on electronics. We can also envisage engineering thin films that will provide each of the colours of the spectrum by simply changing the input voltage, allowing smart paints or smart fabrics whose colour could be chosen to suit mood or environment. We can also develop whose mechanical properties can be actively tuned, which will be useful in medicine and energy applications. In the longer term there is the prospect of developing materials with a negative refractive index, whose special properties would mean that by switching on and off an electric current, objects will apparently disappear and reappear!