In many cases, scientists are not sure what specific ingredient in a particular herb works to treat a condition or illness. Whole herbs contain many ingredients, and they may work together to produce a beneficial effect. Many factors determine how effective an herb will be. For example, the type of environment (climate, bugs, and soil quality) in which a plant grew will affect it, as will how and when it was harvested and processed. In this book we wrote about the perspective of botany and medicinal properties of lemon balm (Melissa officinalis) as medicinal herb.