In an advance, online publication of Science this week, two reports highlight the role of miR-33 in human cholesterol homeostasis. Katey Rayner and her colleagues at the New York University School of Medicine show that miR-33 "modulates the expression of genes involved in cellular cholesterol transport," adding that silencing miR-33 in vivo increases plasma HDL levels. "miR-33 appears to regulate HDL biogenesis in the liver and cellular cholesterol efflux," Rayner et al. conclude.