A rosemary shrub's needle-like leaves have a woody scent. It is not only known as a food seasoning, but also as an aromatic and medicinal plant. An essential oil derived from the plant - which holds its essence and main components - is extracted and sold in small bottles. Many scientists are now exploring the health benefits of rosemary oil because its use in traditional medicine has been documented. Rosemary essential oil is beneficial in improving brain function, stimulating hair growth, relieving pain, easing stress and increasing circulation.