The wheel of rebirth is not only found in changes in the universe; it is also evident in the many changes that people experience during their lifetime, from the time of birth to the time of death. According to scientific research, there is not a single cell in the body that does not change over the course of seven years. In other words, our bodies are completely renewed every seven years. The cellular structure, perception, and cognition of all living creatures, from simple organisms to advanced humans, are constantly moving, changing, living, and dying.
This constant state of flux, renewal, and metabolic change that we experience physically (birth, old age, sickness, and death) and in our minds (the forming, existing, changing, and ceasing of thoughts) are what we call the wheel of rebirth. The wheel of rebirth is also at work in family relationships; at one time we are the children of our parents, yet another time we become the parents of our children. The changes in our economic welfare and the ups and downs of our emotions are also examples of rebirth. Nothing escapes the infinite patterns of change and renewal that are part of the wheel of rebirth.— Master Hsing Yun, Opening the Mind's Eye