Mites as seen under a microscope, from an illustration in Robert Hooke's "Micrographia," published in 1665. Robert Hooke (1635-1703), among many achievements, coined the biological term cell and wrote the book "Micrographia," detailing his observations through his microscope. Mites, along with ticks, are small arthropods belonging to the subclass Acari (also known as Acarina) and the class Arachnida.