Terpenes have very distinct smells, Alpha Pinene for example smells like pine needles & rosemary whereas Beta Pinene smells like dill, parsley and basil, same molecular weight- different spatial arrangement of certain atoms.   See below Alpha and Beta Pinene Molecular Structures:

My personal favorite of terpene rich plants is hops- as a craft beer fan- IPA is super aromatic with the following terpenes:  monoterpene (C10) myrcene and the sesquiterpenes (C15) caryophyllene and humulene (not pictured above).  Most of these terpenes are highly water insoluble and are usually added in as "dry hopped" process. Not to get side tracked but dry hopping involves adding hops to the fermenter or keg after fermentation- in other words not part of the beer boiling process where many essential terpenes are lost.

Besides just smelling fantastic many terpenes have medicinal/health qualities. Aromatherapy uses the medicinal properties of many terpenes to regulate mood, sleep problems, acuity and overall health. it is not a new practice- since 1937 essential oils were known to help burn victims and were thought to have healing powers- however the Egyptians were known to use essential oils long before a French chemist discovered it. Egyptian  medical papyrus considered to date back to around 1555 BC contains remedies for all types of illnesses and the methods of application are similar to the ones used in Aromatherapy and Herbal medicine today.   The Egyptians used a method known as infusion  to extract the oils from aromatic plants and incense was probably one of the earliest ways of using aromatics.  We are still practicing the art of infusion today with all types of carrier oils- MCT, Olive oil, Avocado oil, Mac Nut oil...etc.  To be continued....next topic is how terpenes are delivered as medicine???