Proteomics is a very powerful technique that can be applied to interrogate changes at the protein level. Determining protein function is a key to understanding cellular mechanism. The expression of protein is mostly measured by 2D Gel and Mass spectrometry data analysis. The proteome of various insects have been profiled throughput the complete larval development, different cell lines and organs of insects. This section describes all important proteomic resources developed for various insects including agriculturally important insects. Studying how protein expression is modulated in response to a given set of circumstances, such as infection, disease, developmental stage, senescence or response to drugs, will facilitate the elucidation of many pathways and thus provide a mechanism for diagnosis and therapy.