Abu al-Abbas al-Nabati was an Andalusian botanist during the 1100s whose claim to fame was his development of the scientific method. He used empirical and experimental methods for testing medicines and remedies. He mentored a student, Ibn al-Baitar and taught him his methodical ways.
Ibn al-Baitar left Andalusia and traveled from Africa to Anatolia to study botany, collecting plant samples all along the way. He began his travels in 1219. Five years later, he was employed by an Ayyubid Sultan, al-Kamil, as a chief herbalist. He continued his research in this employ.
Ibn al-Baitar was the first to develop a substantial pharmacopoeia (pharmaceutical encyclopedia) of 1,400 plants, drugs, and foods. It was called Kitāb Al-jāmiʿ fi-mufradāt al-adwiya wa al-aghdhiya. He identified not only how essential oils were made but what certain essential oils could be used for, both the development of costly but effective medicines and for perfume. Specific to his first book, he paid detailed attention to orangewater and rosewater, which were essential oils from the namesake plants.
His second work, Kitāb al-mughnī fī al-adwiya al-mufrada, was an encyclopedia of Islamic medicine. In this book, he went into great detail discussing the use of plants for treating a variety of ailments. Essential oils are a major part of these treatments. Ibn al-Baitar contributed much to the world of essential oils, especially as used in remedies and treatments, before his death in 1248, in Damascus.
Essential oils, as Ibn al-Baitar taught, are generally created through the process of distilling- using steam to extract the oil from the plant. The result is a concentrated hydrophobic liquid. Within the liquid are aroma compounds inherent to the plant from which they were extracted. It is these compounds that make essential oils what they are, potential remedies for various ailments and powerful aromatic agents. This is why the use of essential oils for treatment of medical conditions is called aromatherapy.