The world of the herb is very rich in types and species. Here we will mainly consider their greatest achievements in those herbs that produce essential oils.
To a lesser extent we will consider dye plants (the plants from which we extract colour), aromatics (those rich in aromas or perfumes) and the medicinal plants (the herbs richest in therapeutically active ingredients) together with their younger sisters, the culinary herbs. Naturally these categories are not "exclusive". For example, rosemary can be grown both for the kitchen and essential oils. Depending on the main use that we intend for our herbs we can cultivate in different ways to stimulate the qualities we prefer. To this end we will consider the plant kingdom starting from the essential-oil plants so we might understand its intimate and profound core