Answer:
The periosteum is one source of precursor cells which develop into chondroblasts and osteoblasts that are essential to the healing of bone. Other sources of precursor cells are the bone marrow (when present), endosteum, small blood vessels, and fibroblasts.
Answer: Microscopic organisms are not made of cells.
All things that are living are made of cells.
Cells provide structure for the body. They take in nutrients and convert it to energy as well.