A small cog in a large wheel noun phrase
Used to refer to someone or something that is functionally necessary but has a small significance or importance in a large organization
I decided to leave the firm to set up my own business because I didn't want to be a small cog in a large wheel.
He used to be a small cog in a large wheel before he became our boss.
Used to describe something that has great influence or importance
If you describe something like the great pith and moment, you mean that it is of utmost importance.
Used to indicate the positive or beneficial aspects of someone or something in return for other downsides.
Rich and poor people.
The government has made a great effort to narrow the gap between the haves and have nots.