"When you sow, you do not plant the body that will be, but just a seed, perhaps of wheat or of something else. But God gives it a body as he has determined, and to each kind of seed he gives its own body." NIV translation
Paul continues to use the example of farming to explain about the resurrection body. He explains that it is just as a seed that produces a plant but the plant does not look like the seed. We do not know how or why the seed produces the type of plant that it does.
"Not all flesh is the same: People have one kind of flesh, animals have another, birds another and fish another." NIV translation
As we see in the natural world, God created several kinds of flesh. Although many scientists try to prove that we all evolved out of some slime, one cannot look at the diversity of life and accept that kind of nonsense. All life on this planet testifies to the fact that there is a Creator.
"There are also heavenly bodies and there are earthly bodies; but the splendor of the heavenly bodies is one kind, and the splendor of the earthly bodies is another. The sun has one kind of splendor, the moon another and the stars another; and star differs from star in splendor." NIV translation
Paul goes on to explain that, just like stars and planets are different from each other, we will each have a unique resurrection body. It is comforting to know that we will all still remain unique in heaven.
"So will it be with the resurrection of the dead. The body that is sown is perishable, it is raised imperishable; it is sown in dishonor, it is raised in glory; it is sown in weakness, it is raised in power; it is sown a natural body, it is raised a spiritual body. If there is a natural body, there is also a spiritual body." NIV translation
He goes on to explain that, not only will we each get a unique new body. Our human bodies are amazing in the way that they operate but they are nothing compared to our spiritual bodies that will last forever.
One of the problems in our world today is the fact that people worry too much about trying to make our earthly bodies last forever. We are reminded that, no matter what you do, all of these earthly bodies will one day be corpses left behind.