These are known as Hormones. Hormones are chemical messengers that are released in one tissue normally endocrine glands for example, adrenal glands, pituitary glands, and transported in the blood stream to alter the activities of specific cells in other tissues. Hormones serves as messengers, controlling and coordinating activities or processes such as growth, metabolism and fertility in the body.
Without using the scientific method, it would be much harder to determine a factor that could cause your experiment to fail. By sticking to only one of the methods you could easily destroy your experiment without the background search needed or the materials planned out.
