Question: why do we need marrow?

Luke Williams answered on 16 Mar 2018:

The bone marrow is very very important. It is where all our blood gets made, so without it we would have a problem. The marrow itself is one of the best places to find stem cells in the body, and it is these stem cells that make all the different types of blood cell. You are probably making hundreds of billions of blood cells a day in your marrow. Red blood cells, for example, only last about a month, so continuously need replacing.