What is the significance of bone marrow?

Explanation

### Step-by-Step Solution:

1. **Definition of Bone Marrow**:
- Bone marrow is a soft, spongy tissue found in the cavities of certain bones, particularly in flat bones (like ribs and cranial bones) and at the ends of long bones (like the humerus).

2. **Production of Blood Cells**:
- The primary significance of bone marrow is its role as the site for the production of all blood cells. This includes red blood cells (RBCs), white blood cells (WBCs), and platelets.

...