Plant extracts or essential oils are odorous and highly volatile and have a consistency like water, rather than "oil". They are nature's antiseptics and have various medicinal properties - anti bacterial, analgesic, antiviral and calming.

Plant extracts have healing effects - on a direct physical level because of their ability to increase blood supply to the tissues and thereby relax the body and on an emotional plane, to calm, relax, uplift and invigorate.

Essential oils affect emotions through the senses of smell.  When an essential oil is inhaled it stimulates the olfactory nerves in the nasal passages, which transmit messages - via the olfactory bulb, which decodes aromas to the area of the brain, which then evokes emotions and memory.

Depending on the properties of a particular essential oil, inhalation will induce a specific effect.  For example: to calm, to relax or to uplift.