The development of neutron reflectivity for the study of surfaces and interfaces will be reviewed. The early stages of the development, the associated uncertainties, and the key breakthroughs associated with its application will be charted. Emphasis will be placed upon the importance of the ability to manipulate the refractive index by deuterium labelling, and the impact of this on our understanding of Soft Matter interfaces. Particular emphasis will be placed on the ability to determine detailed structural information and vital compositional data in complex multi-component mixtures. In many ways these developments have all led to the ability to contribute to the study of membrane biochemistry, and could be considered as an ultimate step in the development of the technique.