Neem oil is a pesticide that occurs naturally found in the seeds of the neem tree. Its color ranges from yellow to brown, has a bitter taste, and a garlic/sulfur smell. Neem oil is a mixture of components. Neem oil is a natural byproduct of the neem tree. The oil is harvested from the seeds and leaves of the neem tree. It has been used as a natural pesticide for hundreds of years.