**4. Conclusions**

In the present work, on the example of the hexagonal metal Mg, we attempted a depictive overview to highlight that markedly different deformation mechanisms in anisotropic materials can be quantitatively examined. To do so, it is instructive to choose suited crystallographic orientations for the small scale testing from the bulk of interest, and to avoid mechanical constraints that could promote activation of unintended deformation mechanisms. Furthermore, the crystal reorientation due to twinning and related changes in the preferably activated deformation mechanisms should be kept in mind. Finally, while the mechanical signature and post mortem observations should suffice for analysing the respective deformation mechanisms, direct in-situ observation lends itself to simplify this process significantly and provide better insight into the dynamics and temporal sequence.

**Author Contributions:** Conceptualization, D.K. and S.H.O.; methodology, D.K., J.J., S.H.O.; formal analysis, M.A.; investigation, J.J., M.A., R.K.; writing—original draft preparation, D.K.; writing review and editing, D.K., J.J., M.A., R.K., S.H.O.; visualization, J.J., M.A.; supervision, D.K., S.H.O. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors acknowledge financial support by the Austrian Science Fund FWF (project number I-1020) as well as the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant No. 771146 TOUGHIT). S.H.O. was supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT (MSIT) (NRF-2020R1A2C2101735), the Creative Materials Discovery Program through (NRF-2019M3D1A1078296), Bio-inspired Innovation Technology Development Project (NRF-2018M3C1B7021994).

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

## **References**

