microscope or for more detail an electron microscope
smell can not be measured but can be observed
they can be made into vaccines against themselves. Additionally, virsuses that attack bacteria, called bacteriophages, may someday be used to treat bacteria infections. There has also be research into using viruses to kill harmful insects.
no bacteria is larger than viruses
viruses can be helpful because, some viruses can be used for cures. for example, USA. researcher suggest that adeno-associated viruses type 2 can Promises to be a breakthrough in cancer therapy
a virologist studies viruses