What substance lies between collagen and elastin fibers?

The correct choice is hyaluronic acid, which plays a crucial role in the skin's structure and health. This substance acts as a vital component of the extracellular matrix, which is the network that provides support and anchorage for the cells in the skin. It is known for its ability to retain moisture, which helps to keep the skin hydrated and plump.

Hyaluronic acid is found in the spaces between collagen and elastin fibers, where it contributes to the overall skin elasticity and firmness. By attracting and holding water, it enhances the skin's volume and appearance, making it an essential factor for youthful and healthy skin.

Understanding the role of hyaluronic acid can help in grasping how skin aging and hydration work. It also underscores the importance of incorporating moisturizers and hyaluronic acid products in skincare routines for maintaining skin health.