The parables of the mustard seed and the yeast
These two short parables start with the small beginnings of the Kingdom and point out: (1) its spread throughout the world (Jesus' disciples were small in number, but their message would permeate the world), and (2) its power to transform (yeast works invisibly, but powerfully).
Kingdom Seed: A mustard seed, so small it is almost invisible to the eye, produces a veritable tree capable of housing many birds. In a like manner, the Kingdom, which began so insignificantly, has grown immensely so that it has a huge effect on the world, and it will continue to do so until Christ returns. The Kingdom will reach all nations.
Kingdom Yeast: Yeast works silently and unseen - from the inside - but it affects everything. Though it rises slowly, it has incredible transforming power. Kingdom power is immense, because Gospel yeast truly transforms lives. Thus, the Kingdom of God, on the outside is growing slowly, it may appear almost stagnant at times, but on the inside the Spirit of God is working his will, way, and the consummation of the Kingdom is sure to come to its fullness - to its full expansion.