Watch The Making of clip.
The piece is released under Attribution - Non-Commercial - Share Alike license.
View it on Sketchfab.
2016/02/05: v3 released, with pupils carved in, and a slight shoulder gesture added.
2016/01/20: v2 released, with more detailed hair and moustache, as well as improved likeness.
2014/12/02: v1 released, very rough.
If you're interested in supporting me in sculpting more great scientists, check out my Patreon page.