Another parable put he forth unto them, saying, The kingdom of heaven is like to a grain of mustard seed, which a man took, and sowed in his field: Which indeed is the least of all seeds: but when it is grown, it is the greatest among herbs, and becometh a tree, so that the birds of the air come and lodge in the branches thereof. – Matthew 13.31-32
There are a couple of time when Jesus uses a mustard seed as a picture as an illustration of something that is small and insignificant that has great potential. A little later He will talk about how the tiny bit of faith can do great things.
But here He talks about how the kingdom of God is like a mustard seed that when it is planted seems small and insignificant and like nothing can come of it. Then, one day it will be the greatest plant among herbs big enough for the birds to come and live in the bush.
It may seem to us sometimes in some of our ministries that we have not grown much beyond the size of that mustard seed. But the day is coming when the kingdom of will be the kingdom of all kingdoms when Christ will reign supreme and all earthly powers will fall by the wayside.
God does great things with little thing and He makes great things out of little.