If you keep only one essential oil in the house, make it this one. Organic lavender has the soft, herbaceous floral scent nearly everyone already loves, and it earns its spot on the nightstand: a few drops in the diffuser while you wind down is the simplest bedtime ritual there is.

This is Lavandula angustifolia, USDA certified organic, grown without synthetic fertilizers or pesticides, and bottled undiluted at 10 mL. Three or four drops in 100 mL of diffuser water scent a bedroom; a personal inhaler carries the same calm into the car or the office. Blended at 2 to 5 percent into a carrier oil, it becomes a soothing skin oil, and the maker counts it as a natural first aid kit staple for minor cuts and scrapes. Plant Therapy rates it KidSafe, so it belongs in the kids' room diffuser as much as in your own.