In the Bible: Matthew 13:31-35
Jesus made his way over to a nearby lake where he sat to rest. Soon, a large crowd gathered around him to listen to him speak. Jesus decided people would hear him better if he sat in a boat just off shore, while the people remained on shore. He began telling them many parables to explain heaven and God.
Parable of the Mustard Seed fact:
When Jesus refers to the kingdom of heaven, he is talking about God's family. God's family includes angels and those who trust in Him to save them from certain destruction.
The kingdom of heaven is like a mustard seed. Even though it is the smallest of seeds you plant in your garden, the plant it produces grows large enough to hold birds in it's branches!
The people were amazed at this simple teaching. They hung on every word Jesus said.
Parable of the Mustard Seed fact:
These two parables tell us that God uses even the "smallest" people or objects to expand His kingdom.
In the same way, the kingdom of heaven is like yeast you cook bread with. When you work it into bread dough, it spreads throughout the dough and causes the bread to expand and rise!
All the things Jesus told the people were in the form of a parable, because parables are easier to understand, and generally relate common life happenings.
By speaking only in parables, Jesus was fulfilling the prophecy about him in Psalms 78:
"I will open my mouth in parables,
I will utter things hidden since the creation of the world"
Jesus knew that telling stories is a much more interesting way to teach people difficult ideas or concepts. The people listened to every story, and were amazed at his knowledge and wisdom.