Reflection Anisotropy Spectroscopy (RAS) is a non destructive surface sensitive optical probe capable of operation within a wide range of environments. RAS achieves surface sensitivity by measuring the change in polarisation on reflection of normal incidence light from the surface of a cubic crystal. The technique has been shown to be a sensitive probe of molecular orientation on surfaces@footnote 1,2@ which is capable of monitoring growth at metal/liquid interfaces.@footnote 3,4@ Recent improvements in instrumentation@footnote 4@ have greatly increased the speed of response of RAS equipment so that it can be used to monitor growth at realistic growth rates and to provide information on the orientation and interaction between biological molecules at metal/liquid interfaces on a fast time scale. This talk will present recent results of studies of the physical and electronic structure of metal and semiconductor surfaces and of the RAS of DNA bases and DNA sequences adsorbed at the Au(110)/electrolyte interface. A brief description will be given of how the sensitivity, spectral range and in particular the timescale of RAS will be radically improved by the proposed UK Fourth Generation Light Source (4GLS). @FootnoteText@@footnote 1@J.R. Power, P. Weightman, S. Bose, A.I. Shkrebtii and R. Del Sole, Phys. Rev. Lett. 80 3133-6 (1998).@footnote 2@B.G. Frederick, J.R. Power, R.J. Cole, C.C. Perry, Q. Chen, S.Haq, Th. Bertrams, N.V. Richardson and P. Weightman. Phys. Rev. Lett. 80 4490-3 (1998).@footnote 3@B. Sheriden, D.S. Martin, J.R. Power, S.D. Barrett, C.I. Smith, C.A. Lucas, R.J. Nichols and P. Weightman, Phys. Rev. Lett. 85 4618-21 (2000).@footnote 4@P. Harrison, T. Farrell, A. Maunder, C.I. Smith and P. Weightman, Meas. Sci. Technol. 12 2185-91 (2001).