What are the BIG questions??

[mitton at mitton.ip.portal.com]

Richard Feynma's thesis mentor advised him to figure out what are the biggest 
mysteries in particle physics and then spend your time trying to unravel it.

I spent several years working as a physics technician and am now a cell bio. 
undergrad. I'm learning tons of stuff about what is known but nothing about 
what is not known. (I've already decided that if I'm ever a prof I'm going to 
teach a course titles "What we have no idea about in cellular biology")

What are the big questions in cell/micro/molecular bio? Any opinions?

Thanks.