Both expression and functional proteomics have been applied to identifying and characterizing human milk proteins. The most extensive expression work, resulting in more than 107 identified proteins reported in an annotated database, was done on the proteins associated with the milk fat globule membranes of human colostrum. Reports on the differences in protein expression between colostrum and mature milk and on the relationship between the mother’s diet and protein milk composition may be regarded as functional proteomics studies. Future studies of the human milk proteome will be beneficial for both lactating mothers and nursing children.