Origin of Quantum Mechanics [Discussion]

A lot of CEans here must be intrigued by the topic of "Quantum Mechanics". I've seen that some of us engineers here are interested in the threads related to quantum physics, or quantum theory, that branch of physics which deals with physical phenomena at microscopic scales.
But when you think about it, a question may occur to a curious mind. How did it all began? Why did scientists and researchers begin studying this stuff and came up with the concept of 'Quanta' or 'Quantum Mechanics'.

I found an interesting video that simplifies the concept and shares the exact origin of Quantum Mechanics -




Do watch it and share your opinions and questions here.