What are windows to earths interior?

Answer 1

Mantle-derived xenoliths.

The magma is mantle and/or subducted-crust-derived.

Xenoliths come from the country rock through which the magma rises, so really it's the magma (solidifying as igneous rock) that's the window.

For greater depths, seismic analysis is the window.

Answer 2

Windows to Earth's interior include seismic waves, volcanic eruptions, and geothermal energy sources. By analyzing seismic waves generated by earthquakes, scientists can study the composition and structure of the Earth's interior. Volcanic eruptions provide a glimpse into the molten material beneath the Earth's surface, while geothermal energy sources showcase the heat produced by the Earth's interior.