This book sheds new light on the role of various environmental factors in regulating the metabolic adaptation of medicinal and aromatic plants. Many of the chapters present cutting-edge findings on the contamination of medicinal plants through horizontal transfer, as well as nanomaterials and the biosynthesis of pharmacologically active compounds. In addition, the book highlights the impacts of environmental factors (e.g., high and low temperature, climate change, global warming, UV irradiation, intense sunlight and shade, ozone, carbon dioxide, drought, salinity, nutrient deficiency, agrochemicals, waste, heavy metals, nanomaterials, weeds, pests and pathogen infections) on medicinal and aromatic plants, emphasizing secondary metabolisms.