**5. Conclusions**

Intense and short X-ray FELs allowed new understanding of the interaction and response of C60 fullerenes in a new energy regime. Furthermore, FELs facilities offer the possibility to carry out time-resolved experiments that allow us to extract molecular movies of the system's transformation as it evolves as a function of time. Future work could focus on using shorter X-ray pulses, for example, *as* pulses, as well as using other experimental methodologies, such as electron spectroscopy, coincidence techniques or ultra-fast electron diffraction. The combination of X-ray *as* FEL facilities and differential experimental techniques will enable scientists to understand the first steps in the photoabsorption or scattering investigations, resulting in new breakthrough that will push the frontiers of science and may result in new discoveries.

**Funding:** This work was funded in part by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy, gran<sup>t</sup> No. DE-SC0012376.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable. **Data Availability Statement:** The data can be made available if requested.

**Acknowledgments:** We thank A. Sanchez-Gonzalez, Z. Jurek, R. Obaid, H. Xiong, R.J. Squibb, T. Osipov, A. Lutman, L. Fang, T. Barillot, J.D. Bozek, J. Cryan, T.J.A. Wolf, D. Rolles, R. Coffee, K. Schnorr, S. Augustin, H. Fukuzawa, K. Motomura, N. Niebuhr, L.J. Frasinski, R. Feifel, C.P. Schulz, K. Ueda, K. Toyota, S.-K. Son, K. Ueda, T. Pfeifer, J.P. Marangos, B.F. Murphy, L. Avaldi, P. Bolognesi, C. Bostedt, J. Eland, M. Guehr, J. Farrell, J. Glownia, D.T. Ha, K. Hoffmann, E. Kukk, B. McFarland, C. Miron, M. Mucke and R. Santra.

**Conflicts of Interest:** The authors declare no conflict of interest.
