The applications of insect protein expression systems include: functional assays, expression of intracellular proteins, expression of protein complexes, structural analysis, and virus production. Insect cells work efficiently for production of virus-like particles, which are non-infectious particles that resemble viruses and lack genetic material. These particles can be used to develop vaccines or be used as tools to study viral structure and immune responses. Additionally, these systems have the ability to co-infect insect cells with multiple recombinant baculoviruses, which allows for the generation of different protein subunits.