Kathi Keville has been teaching and writing about herbal medicine, aromatherapy, herb gardening, and ethnobotany for more than four decades. Her seminars are presented throughout North America, including at her Green Medicine Herb School at Oak Valley Herb Farm in Nevada City, California.

Her fourteen books include the newly revised Aromatherapy: The Complete Guide to the Healing Art. She has also written 150 magazine articles and consulted for numerous magazines, such as National Geographic, Newsweek, and Woman's Day. Kathi can be heard on The Garden Forum- Herbal Edition on KVMR Radio, and as co-host on the aromatherapy show Everybody Knows on Veria Holistic Health Channel.

Christopher Hobbs, PhD, LAc, is the author of Christopher Hobbs's Guide to Medicinal Mushrooms. He is an internationally renowned mycologist, herbal clinician, licensed acupuncturist, botanist, and research scientist with over 40 years of experience in herbal medicine. The author of more than 20 books, he lectures on herbal medicine worldwide. Hobbs has taught at universities and medical schools such as Stanford Medical School, Yale Medical School, Bastyr University, UC Berkeley, and the National School of Naturopathic Medicine. He lives in the Sierra foothills of California.