It's old? dating back to 2010 but it's an interesting and very educative article about some secretive parts of our planet

It is pitch black, icy cold and the pressure is phenomenal. The deepest parts of the ocean are some of the least hospitable places on Earth - yet footage from recent expeditions reveals that life in the oceanic trenches is thriving.

http://news.bbc.co.uk/2/hi/8426132.stm