The achievement is a breakthrough in biomedical engineering that could lead to replacement lungs for humans in the near future, experts say.

Currently, the only way to replace diseased lungs in adults is a lung transplant, a high-risk procedure that's vulnerable to tissue rejection.

In a new study, researchers took lungs from a living rat and used detergents to remove lung cells and blood vessels, revealing the organ's underlying matrix.

This lung "skeleton"—made of flexible proteins, sugars, and other chemicals—consists of a branching network that divides more than 20 times into smaller and smaller structures. (See an interactive graphic of lung structure.)

The researchers placed these "decellularized" lungs into a bioreactor, a machine filled