With many such parables he spoke the word to them, as they were able to hear it.  He did not speak to them without a parable, but privately to his own disciples he explained everything.
(Mark 4:30-34 ESV)
This imagery struck me this morning.
The kingdom of God is like this tiny mustard seed... so small it is insignificant. Yet it grows to be the biggest plant you can imagine.
I read this and think of how God moves in the heats of people. My son and I are reading through a missionary book and in it they speaks of a young man who is helping them translate the Bible and he is not a believer. Then one day he hears of how Jesus stands at our door (of our heart) and knocks and that simple phrase opens his eyes to the truth of the gospel. Just a small thing and his whole life is changed.
Blows me away sometimes if I just stop to think about how God works.
Can he use the big things? FOR SURE.
But often it's those little things that make people stop and take notice of the truth of the gospel. The neighbour always willing to help out, the caring given, the words spoken, the steadfastness demonstrated....God uses those small things that we do to change the world.
When you put all those small things together... consider the size of the God's kingdom. All the Christians that ever lived and are living still. Started with small things that opened eyes and changed hearts.
That's the Kingdom of God!
Jesus painted all these word pictures for those who came to hear him talk. He explained those word pictures to those who stuck by his side...those disciples of his. He helped them understand all he talked about, and for the rest he just told parables to. He gave his public message and later his private deeper teaching.
I know...not a full picture and not how all churches do it. But It's like having a mentoring relationship with someone. Taking a full message and then breaking it down into deeper understanding.