Flower essences are infusions of flowers in water, processed with brandy or vinegar. These remedies are profound but gentle medicines that treat the emotional, psychological and vibrational (nanoparticle) level much as homeopathic remedies do.
Although used for centuries, they were brought to the Western culture of today by the British medical doctor, Dr. Edward Bach; who then left his medical practice to devote his life to studying and developing 38 Bach Flower remedies of which Rescue Remedy, used for shock and trauma, may be the best known.
Today, there are many reputable companies and practitioners studying this gentle but powerful form of plant medicine, as we come to understand that we are more than out cells; that these cells have an detailed and complex community network called the extracellular matrix and many cell receptors communicate as part of this matrix with not only chemical messengers but at the nanoparticle level.
Some of the companies that I like for flower essences in addition to Bach Flower are Delta Gardens, Avena Botanicals and Woodland Essences. You can also study and learn how to make your own essences.
The Flower Essence Service out of Nevada City California is a great resource at https://www.fesflowers.com/.