The Mössbauer effect is a useful tool for the determination of the static and the dynamic structure of biomolecules. This contribution concentrates on the study of the dynamical properties by the measurement of the Lamb Mössbauer factor in a large temperature range. Investigations on myoglobin are discussed in detail. The experimental results indicate that above 200 K a new motional degree of freedom appears in addition to the usual vibrations. It may be attributed to fluctuations between slightly different conformational substates of the molecule