Insects have dominated the terrestrial planet for more than 350 million years. While entomologists have recognized and named more than one million different species of insects, experts vary widely on the true number of insects species-with estimates ranging as widely as from 3 to 30 million unique species. At any given moment, 200 million insects live for every human on Earth, over 70 percent of all animal species are insects. They have achieved something that has eluded humans-sustainable development. Insects are the primary consumers of plants, yet they are also the dominant pollinators, thus ensuring plant reproduction. They play a critical role in disease transmission yet the service they provide to ecological maintenance is unparalleled.<br><br>Entomologists conduct insect-based research in numerous areas ranging from general biology, natural history, systematics, ecology and behavior, to molecular biology, physiology and development, to medical and agricultural entomology. Emerging areas include invasive species, biodiversity, pollination ecology, forensics, global health, and genomics. Entomology is a very specific discipline, yet at the same time, an immensely broad and diverse field of study touching a wide array of other subjects. As such, entomological training provides many choices and opportunities for those interested in the diversity of nature. While some entomologists work in the field, others work in the laboratory or classroom. Students majoring in entomology study in a variety of fundamental and applied fields. Graduates find employment in college and university teaching, research and extension work, state and federal government service, industry, and research institutes.