This is the atomic resolution top-down structure of the neuraminidase protein found on the surface of the Influenza virus (individual spheres represent individual atoms). Neuraminidase is the protein, along with haemagglutinin which allows for the nomenclature of naming strains of Influenza (i.e. H1N1). These are key proteins used by the virus to establish and maintain infections, and also mutate at a rapid rate which is why you need a new flu vaccine every year (P.S. it is flu season, get vaccinated!). In this image of neuraminidase, the yellow spheres make up amino acids within the protein sequence that are commonly mutated, whilst the other colours depict those amino acids that are conserved. As you can see, there is a lot of yellow here, and so there is very little conservation of amino acids in this protein between strains, which presents a challenge to drug and vaccine design.
Image courtesy of Professor Peter Colman , Division head of Structural Biology at the Walter and Eliza Hall Institute in Melbourne, Australia.