What is a flash cube?

My first camera required flashcubes and a 126 film cartridge... early to mid 1970's..

I remember everyone marvelling at the latest innovative and very convenient invention.

I used. to work in a photo lab. it was a very interesting job. now it is all digital and my skill is now obsolete. now a darn computer does the deciding about adding color to highlight the subject. diana in seattle.