A phenome is the set of all phenotypes expressed by a cell, tissue, organ, organism, or species. A phenome includes phenotypic traits due to either genetic or environmental influences. Just as the genome and proteome signify all of an organism's genes and proteins, the phenome represents the sum total of its phenotypic traits. Some examples of human phenotypes are skin color, eye color, height, or specific personality characteristics. Phenotypic differences between individuals can be due to environmental influences, genetic variation such as single nucleotide polymorphisms (SNPs), or a combination of the two. Phenomics is the study of the nature of phenotypes and how they are determined, particularly when studied in relation to the set of all genes (genomics) or all proteins (proteomics).