He told them still another parable: "The kingdom of heaven is like yeast that a woman took and mixed into a large amount of flour until it worked all through the dough." (Matthew 13:33)

Yeasts are even smaller than seeds. We know - at the time of Jesus it was impossible to know - that yeast cells are 5-10 micrometres in diameter.

Yet yeast will totally transform the dough. The same wild yeasts can ferment wine and beer.

Historians speculate that yeast was originally discovered when a mixture of meal and water was left longer than usual on a warm day. The natural contaminants in the meal began fermenting. When the dough was baked the transformation was complete.

It was a mysterious, even miraculous result. How it happened or why was in those days entirely beyond knowing.

Gradual, even incremental, and very surprising: such is the kingdom of heaven.

But for the yeast to fully transform the large amount of flour in the parable, the woman had to work it through and through.

The kingdom of heaven depends on our contributions too.