In human cells, there are more than 30,000 proteins. In order for the cells to become organized and exert higher order functions, the proteins must be properly sorted into the various cell organelles. Figure shows mitochondria (red) and ER (green) observed using fluorescent microscopy. We are working on sorting proteins and integrating membrane proteins in animal cells. The followings are some of the questions we seek to answer through our study. How are membrane proteins correctly integrated into the ER membrane? How are peroxisomal membrane proteins targeted to peroxisomal membrane instead of ER membrane?