I was awarded my PhD at Lund University in 1967; my thesis dealt with the effects of light on plastid differentiation in plant roots. I think that it was my father who put me on the biology track, mostly by showing me small animals and what they are up to: ants, ant lions, Daphnia etc.

Mostly, I am driven by curiosity, but now and then I have had practical goals in sight: saving the ozone layer, finding a way of early detection of plant disease, finding a recipe for optimum exposure to sunlight (avoiding skin cancer and other damage, while still getting enough vitamin D).

My current projects deal with three topics:

1. Evaluation of how the ozone depletion during the years 1974–2000 has affected terrestrial plant productivity.
2. How does thermal (mid-infrared) emissivity of the eggshell affect the optimum allocation of time (for birds) between foraging and egg incubation? When birds leave the nest, eggs start to cool, and they cannot be allowed to cool below a critical temperature without damage. Cooling rate is dependent on infrared emissivity (among other factors).
3. The discovery of photoreactivation is generally ascribed to K.W. Hausser and H. v. Oehmcke (1933), but can their observations be explained in another way? Could it be explained as gene regulation?

In the future, I would like to continue to find out what the optimum sunlight exposure for people is under various conditions. We have made a small start [e.g.,McKenzie, R.L., Liley, J.B. and Björn, L.O. (2009) UV radiation: Balancing risks and benefits. Photochemistry and Photobiology 85, 88–98 , and Norval, M., Björn, L.O. and de Gruijl, F.R. (2010) Is the action spectrum for the UV-induced production of previtamin D3 in human skin correct? Photochem. Photobiol. Sci. 9, 11-17 ], but we need more reliable information for a "recipe" that can be recommended to people.

I am a member of UNEP's "Environmental Effects of Ozone Depletion Panel" almost since its start after the Montreal Protocol. On this panel I have contributed particularly to the chapters on "Changes in biologically active ultraviolet radiation reaching the Earth's surface" and "Terrestrial Ecosystems", but also a little to other chapters such as "Health" (in the latter case regarding vitamin D synthesis). I am currently also a member of the EU supported consortium "UV4growth, COST-Action FA0906" (COST stands for European Cooperation in Science and Technology). Within this project I have organized a course in Szeged and coauthored "Handbook and good practice recommendations for research on the effects of ultraviolet radiation on plants".

Currently, my main hobby is insect photography. I like to tinker with home-built equipment, such as "The Amateur Scientist's Spectrophotometer" described in Chapter 25 of my book "Photobiology, The Science of Life and Light" (see publication list). I am now trying out a device for measuring infrared (thermal) emissivity.

I am half-time employed a professor at the South China Normal University. My activity there is described (in Chinese) and I am introduced (in English). One of my English-language lectures in China is reproduced at http://v.youku.com/v_show/id_XMjAzODYzMTg0.html