Is there anything science should not try to explain? Science is knowledge and knowledge is power - power to do good or evil. Sometimes ignorance is bliss.
The greatest grand challenge for any scientist is discovering how to prevent the spread of HIV and finding the cure or an effective vaccine for AIDS.
I always start with characters rather than with a plot, which many critics would say is very obvious from the lack of plot in my films - although I think they do have plots - but the plot is not of primary importance to me, the characters are.

