If you describe something as a building block of something, you mean it is one of the separate parts that combine to make that thing.
...molecules that are the building blocks of all life on earth. [+ of]
building block in British English
noun
1.
a block of stone or other material, larger than a brick, used in building
2.
a component that fits with others to form a whole
standardized software building blocks
3. another name for (the child's toy) block
Examples of 'building block' in a sentence
building block
It was the most important building block of society and therefore above question.
Knowles, Jane Know Your Own Mind (1991)
It should be the building blocks towards something permanent.
The Sun (2008)
It is too important a building block of society to be made the subject of a crass publicity stunt.
The Sun (2006)
Protein - one of the building blocks of body tissue.
The Sun (2016)
This was pursued as follows: "The family is the building block of society.
Langan, Mary (ed) Taking Child Abuse Seriously: Contemporary issues in child protection theory andpractice (1990)
As well as being one of the building blocks of national economic stability, they have the capacity to deliver incentives for hard and loyal employment.
Times, Sunday Times (2006)
You have to fight to move forward, that's one of the building blocks for a good team.
Times, Sunday Times (2007)
In other languages
building block
British English: building block NOUN
If you describe something as a building block of something, you mean it is one of the separate parts that combine to make that thing.
...molecules that are the building blocks of all life on earth.