The concept of Proteome was first proposed by Marc Wilkins, referring to all proteins expressed by a genome, or a cell or tissue. There are differences between the concept of a proteome and the concept of a genome, which varies with the organization and even the state of the environment. At the time of transcription, a gene can be spliced in multiple mRNA forms. A proteome is not a direct product of a genome, and the number of proteins in a proteome can sometimes exceed the number of genomes. Proteomics is in an early "developmental" state, and experts in this field deny that it is a simple methodology, just like genomics, not a closed, conceptually stable system of knowledge, but an area.