33 Jesus also used this illustration:
The Kingdom of Heaven is like yeast used by a woman making bread.
Even though she used a large amount of flour, the yeast permeated every part of the dough.
Baker's yeast, a single celled fungi, is the common name for the strains of yeast commonly used as a leavening agent in bread, where it converts the fermentable sugars present in the dough into carbon dioxide & ethanol. (Wikipedia)
That's what makes dough rise or get bigger.
Yeast is what it is. Though it is of the simplest forms of life, it's ability to spread within a lump of dough is quite compelling & unstoppable.
Why did Jesus use this parable?
Could it be that He was saying that no matter where we find ourselves, we as His followers will permeate the place in which we live & do life for Him.
That by our very nature as a person connected to God, we will cause people to connect to God also simply because they are around us & see God in us.
Is that a bit of a stretch, or does that makes sense?