Viruses show different morphologies in their shapes and sizes. These are smaller in structures than the bacteria. Though these are simpler as an individual, when formed in group they are exceptionally diverse both in replication strategies and structures. Many viruses are important human pathogens. Many techniques such as x-ray crystallography, NMR and cryo-EM are used to determine viral structures. These structure in-turn are used to develop anti-viral drugs and vaccines.