All solid surfaces in contact with biological systems form a protein corona and the nature of this corona determines the further response of the biosystem to that solid surface (or particle). A number of factors are known to be involved in the formation of the corona, diffusion rates, protein exchange, variation of the surroundings with time, rearrangement of the protein on the surface. However, the process is not well characterized or understood. An important issue is the extent to which two proteins compete and/or cooperate in their adsorption and the time dependence of these processes. Neutron reflectometry is able to distinguish some of the features of mixture adsorption by making use of its structural resolution and using appropriate variation of the external conditions. We propose to study mixtures of lysozyme and human serum albumin, focussing especially on short time changes.