Bone marrow comes in two colors: red and yellow.
Red Bone Marrow
Red bone marrow is responsible for producing blood cells. It contains blood stem cells that develop into red blood cells, white blood cells, and platelets. At birth, all bone marrow is red. However, as we age, a significant portion converts to yellow marrow. [Source: Definition of bone marrow - NCI Dictionary of Cancer Terms - NCI, https://www.cancer.gov/publications/dictionaries/cancer-terms/def/bone-marrow; Bone Marrow: What it is & Why it is Important, https://my.clevelandclinic.org/health/body/22818-bone-marrow; Red Bone Marrow Vs. Yellow Bone Marrow | Peconic Bay Medical ..., https://www.pbmchealth.org/news-events/blog/red-bone-marrow-vs-yellow-bone-marrow]
Yellow Bone Marrow
Yellow bone marrow is primarily composed of fat and contains stem cells capable of becoming cartilage, fat, or bone cells. It's often found in the medullary cavity of long bones, frequently surrounded by a layer of red bone marrow. [Source: What Is Bone Marrow? | Moffitt | Moffitt, https://www.moffitt.org/treatments/blood-bone-marrow-transplant/what-is-bone-marrow/; Bone Marrow: What it is & Why it is Important, https://my.clevelandclinic.org/health/body/22818-bone-marrow]
The Transition from Red to Yellow Marrow
Approximately half of a person's red bone marrow is converted to yellow marrow by the age of seven. [Source: Red Bone Marrow Vs. Yellow Bone Marrow | Peconic Bay Medical ..., https://www.pbmchealth.org/news-events/blog/red-bone-marrow-vs-yellow-bone-marrow]
