Banks

Personally, I like to juice up several different kinds of fruit and vegetables - which may include various combinations of bananas, red bell peppers, apples, carrots, celery, broccoli, spinach, parsley, tomatoes, cucumbers, etc.

By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning.