Of the classical compartments of eukaryotic cells, peroxisomes were the last to be discovered. They are small, single-membrane-bound vesicles involved in cellular metabolism, most notably the beta-oxidation of fatty acids. Characterization of their properties and behavior has progressed rather slowly. However, during the past few years, peroxisomes have entered the limelight as a result of several breakthroughs. These include the observations that they are not autonomously multiplying organelles but are derived from the endoplasmic reticulum, and that partitioning of peroxisomes to progeny cells is an active and well-controlled process. In addition, we are discovering more and more proteins that are not only dedicated to peroxisomes but also serve other organelles.