Earth laughs in flowers. - Ralph Waldo Emerson
Aromatherapy is a form of alternative medicine that uses plant materials known as essential oils and other aromatic compounds for the purpose of altering a person's mind, mood, cognitive function or health. (via Wikipedia)
Personally, I love aromatherapy because I do find that it makes me calm. There are certain scents that are meant evoke certain emotions.
A few examples are cinnamon, lavender, peppermint, and lemon. Cinnamon is supposed to be warming, while peppermint is relaxing. Lemon is uplifting and refreshing and lavender is soothing and calming.
Common uses of these essential oils are either as room sprays, added to unscented lotions, and even added into washing machines. Make sure you don't use pure essential oil straight on your skin because it can be harmful, and definitely do not ingest any of the oils. Happy experimenting!