The seed within me, within you, everyone,the seed is there. And as soon as the seed takes place in the mother's womb, the seed begins to fructify, little by little. Then it comes out. When it is properly developed with hands and legs and eyes, it comes out from the mother's womb. Then again develops, again develops. He becomes a boy, he becomes a youth,he becomes a... So many things, changes everything. But that seed is permanent. The body is changing, but the seed is there. Therefore it is sanatana. It is very easy to understand how we change our body. We are changing our body every moment, imperceptibly. Imperceptibly, we are changing our body every, every moment, every second. So change of body is a fact. Therefore that bijam, that small particle, spark of spirit, that is sanatana. This body is changing. Now, when it is changed to another body, that means transmigration of the soul from one body to another. This is a fact, and it is not very difficult to understand. We are changing our body every moment-Srila Prabhupada