Essential Oils: Nature’s Precious Gift Have you ever wondered what is the reason of perfume in flowers and other plant parts? They are the essential oils. But in addition to the aromatic part, the essential oils also contain plant hormones and some other compounds. The essential oils are highly effective at very low concentrations. They have considerable effects on plants, animals as well as insects. The main reason of this is that the essential oils are very ancient compounds that were produced by the very ancient plants and have been produced ever since. The animals existed with the plants from the beginning. This long term of co-existence has caused them to respond to these essential oils in some way or the other.