 Microbiology is the study of microorganisms, those being unicellular single-cell multicellular cell colony or acellular lacking cells. Microbiology encompasses numerous sub-disciplines including virology, parasitology, mycology and bacteriology. Eukaryotic microorganisms possess membrane-bound cell organ-hells and include fungi and protists, rasprocariotic organisms all of which are microorganisms are conventionally classified as lacking membrane-bound organ-hells and include bacteria and archaea. Microbiologists traditionally relied on culture, staining, and microscopy. However, less than one percent of the microorganisms present in common environments can be cultured in isolation using current means. Microbiologists often rely on molecular biology tools such as DNA sequence-based identification, for example 16S-au-Ren-A gene sequence used for bacteria identification. Viruses have been variably classified as organisms, as they have been considered either as very simple microorganisms or very complex molecules. Microbions, never considered as microorganisms, have been investigated by virologists, however, as the clinical effects traced to them were originally presumed due to chronic viral infections, and virologists took search discovering infectious proteins. The existence of microorganisms was predicted many centuries before they were first observed, for example by the Jains in India and by Marcus Tarendi Eusebara in ancient Rome. The first recorded microscope observation was of the fruiting bodies of molds, by Robert Hook in 1666, but the Jesuit priest Abinatius Kircher was likely the first to see microbes, which he mentioned observing the milk and putrid material in 1658. Anton Yevan-Levin Hook is considered a father of microbiology as he observed and experimented with microscopic organisms in 1676, using simple microscopes of his own design. Scientific microbiology developed in the 19th century through the work of Louis Pasteur and in medical microbiology Robert Koch.