**5. Concluding remarks**

As the instrumentation for IXS is improved, it became possible to carry out many *Q-E* scans in a relatively short time, covering wide *Q-E* space. This enables us to convert the dataset of the dynamic structure factor *S*(*Q*, *E*) into the van Hove function *G*(*r*, *t*) which describes dynamics in real space and time. This new capability allows us to visualize local dynamics directly rather than through the modeling for *S*(*Q*, *E*). Even though the van Hove function is just the Fourier transform, in order to determine it, we have to measure *S*(*Q*, *E*) over a wide *Q-E* space, which forces us to collect much more information than we normally do. This alone brings us to a new territory. Furthermore, by visualizing it, we gain much intuition. For instance, the behavior of the first and second peaks of water shown in **Figure 3** was totally unexpected. Only after seeing it, we understand right away what this means, but no one would have anticipated it before it is seen. It is fully expected that such surprises will occur when this approach is applied further to the study of local dynamics in liquids, glasses, and soft matter in general.
