So far, researchers have found that there are as many as 40 types of growth factors contained in embryos and thymus tissues, many of which have been proven to be the target tissues for skin growth, and have important regulatory and promoting effects on skin cell metabolism and division and reproduction. If these growth factors can be filled into the skin tissue of middle-aged people by applying a cream, it will have a certain effect on maintaining the health of skin tissue and delaying skin aging. An accurate understanding of this text is:. ['Creams containing growth factors have the potential to maintain skin health.', 'Researchers find more than 40 growth-protecting growth factors.', 'Middle-aged people are most effective with creams containing growth factors.', 'An effective way to delay skin aging is to apply a cream containing growth factors.']