Explanation:

- Boeing unveiled a material called Microlattice in 2015.

- It's one of the world's lightest materials.

- Despite its lightness, it's very strong and durable.

- This makes it suitable for various applications, particularly in aerospace.

- Molybdenum is a metal known for its high melting point and strength.

- It's not lighter than air, nor associated with Boeing's development.

- Titanium is a strong, lightweight metal often used in aerospace.

- It doesn't possess the specific properties described for Microlattice.

- Iridium is a dense, very hard metal.

- It's nowhere near as light as Microlattice.