what is use of cryogenics in virology ?

Nuclear magnetic resonance (NMR) is one of the most common methods to determine the physical and chemical properties of atoms by detecting the radio frequency absorbed and subsequent relaxation of nuclei in a magnetic field. This is one of the most commonly used characterisation techniques and has applications in numerous fields. Primarily, the strong magnetic fields are generated by supercooling electromagnets, although there are spectrometers that do not require cryogens. In traditional superconducting solenoids, liquid helium is used to cool the inner coils because it has a boiling point of around 4 K at ambient pressure. Cheap metallic superconductors can be used for the coil wiring. So-called high-temperature superconducting compounds can be made to super conduct with the use of liquid nitrogen, which boils at around 77 K.
Magnetic resonance imaging (MRI) is a complex application of NMR where the geometry of the resonances is deconvoluted and used to image objects by detecting the relaxation of protons that have been perturbed by a radio-frequency pulse in the strong magnetic field. This is most commonly used in health applications.
In large cities, it is difficult to transmit power by overhead cables, so underground cables are used. But underground cables get heated and the resistance of the wire increases, leading to waste of power. Superconductors could be used to increase power throughput, although they would require cryogenic liquids such as nitrogen or helium to cool special alloy-containing cables to increase power transmission. Several feasibility studies have been performed and the field is the subject of an agreement within the International Energy Agency.

Cryogenic gases delivery truck at a supermarket, Ypsilanti, Michigan
Cryogenic gases are used in transportation and storage of large masses of frozen food. When very large quantities of food must be transported to regions like war zones, earthquake hit regions, etc., they must be stored for a long time, so cryogenic food freezing is used. Cryogenic food freezing is also helpful for large scale food processing industries.
Many infrared (forward looking infrared) cameras require their detectors to be cryogenically cooled.
Certain rare blood groups are stored at low temperatures, such as −165 °C, at blood banks.
Cryogenics technology using liquid nitrogen and CO2 has been built into nightclub effect systems to create a chilling effect and white fog that can be illuminated with colored lights.
Cryogenic cooling is used to cool the tool tip at the time of machining in manufacturing process. It increases the tool life. Oxygen is used to perform several important functions in the steel manufacturing process.
Many rockets use cryogenic gases as propellants. These include liquid oxygen, liquid hydrogen, and liquid methane.
By freezing the automobile or truck tire in liquid nitrogen, the rubber is made brittle and can be crushed into small particles. These particles can be used again for other items.
Experimental research on certain physics phenomena, such as spintronics and magnetotransport properties, requires cryogenic temperatures for the effects to be observed.
Certain vaccines must be stored at cryogenic temperatures. For example, the Pfizer–BioNTech COVID-19 vaccine must be stored at temperatures of −90 to −60 °C (−130 to −76 °F). (See cold chain.)

Certain vaccines must be only stored at cryogenic temperature (ultra low temperatures of order -90 to -60 degree celcius / -130 F to -76 F)