THP-1 monocytes were treated at a cell density of 1 × 106 cells/mL for 3 hours. Monocytes were fixed in 1% paraformaldehyde and lipid droplets were stained with Oil Red O. Monocytes were observed at room temperature using a Zeiss Axioskop2 plus microscope with a Pan-Neofluar 40× objective, 1.3 oil. DIC images were captured using a Zeiss AxioCam MRm camera and processed using AxioVision LE software. (A to C) Negative controls included (A) media, (B) LpL (2 U/mL), and (C) VLDL alone (200 mg TG/dL), and resulted in low levels of droplet formation. (D) VLDL lipolysis products (200 mg TG/dL VLDL + 2 U/mL LpL) induced formation of droplets that stained red with Oil Red O, indicating that they are lipid-filled. Cells from each treatment were analyzed over a minimum of 10 frames per experiment. The experiment was repeated 3 times, with similar results. Arrows, lipid droplets. Original magnification ×400 for panels A–D.