Bone Marrow

right|300px  
Most bones in the human body contain marrow. It can be either red or yellow. it is the flexible tissue found in the interior of bones.
==Red Marrow==
if bone marrow is red, it contains mainly blood tissue.
==Yellow Marrow==
if bone marrow is yellow, the fat tissue out numbers the blood tissue.
==Trivia==
*all bone marrow is red when you are first born.
*as you get older, more and more turns yellow.
*On average, bone marrow constitutes 4% of the total body mass of humans.