Books, posters, sheet music

The transcript discusses the world's largest movie library, managed by the Museum of Modern Arts Film Research Staff. They are compiling an encyclopedia of cinema, adding new material daily. This collection serves as a vital resource for understanding the young art of cinema, whose history spans only a few decades.

In what way is the collection described as an important source material?

What can be inferred about the timeline of the art's history based on the text?