missing link
idiomPart oflinking
missing link — idiom
1. something that is needed to complete a series or to solve a problem by providing
1.idiom
Definition
something that is needed to complete a series or to solve a problem by providing the connection between two known things
Example
The discovery of the fossil provided the missing link between ancient reptiles and modern birds.
For years, scientists searched for the missing link in the theory of how cells divide.