How should I understand "She cracked open a door"?

I learned the following sentence from 100 Greatest Science Discoveries of All Time by Kendall Haven:

Marie Curie's studies rank as one of the great turning points of science. Physics after Curie was completely different than before and focused on the undiscovered subatomic world. She cracked open a door that penetrated inside the atom and has led to most of the greatest advances of twentieth-century physics.

I don't understand the sentence in bold. Why can two verbs, "cracked" and "open", be put together in this sentence? Or do I misunderstand the part of the speech here?

It's not two verbs, cracked and open. It's one phrasal verb, crack open. Open is the particle (open can be an adjective and an adverb, as well as a verb), and crack is the verb.

To crack means to make a crack, or opening, in something, which can be literal, like crack an egg, or figurative, like crack the books (which means study) or crack another bottle of scotch, which means to open a sealed bottle.

The phrasal verb crack open means to open something sealed (like a door) a very small amount ("only a crack"), so that one can see inside. It refers to the very beginning of an opening.

In this case, it's metaphoric, and refers to the first "opening" of scientific knowledge of the atom, which was due to Curie's work.