Who named the material of the nucleus chromatin?

The material inside the nucleus was named “chromatin” by the scientist Walther Flemming.

Explanation:
In the late 19th century, Walther Flemming, a German biologist, used dyes to study cells under a microscope. He noticed that a special thread-like material inside the nucleus absorbed the dyes and became easily visible. Because this material took up stain (or colour), he called it “chromatin”, where “chroma” means colour in Greek. Chromatin is now known to be made of DNA and proteins, and it helps in storing genetic information in cells.