Cover picture: Cytoskeleton organization in undifferentiated human mesenchymal stem cells (top row) and mature human osteoblasts (bottom row). In these confocal images, actins and tubulins are stained with rhodamine-phalloidin (red) and FITC-conjugated anti-α-tubulin antibody (green), respectively. Undifferentiated stem cells (top left) demonstrate numerous thick actin stress fibers, unlike thinner actin filament meshwork observed in osteoblasts (bottom left). In response to the treatment of cells with 5 mM cytochalasin D and 5 mM nocodazole, the cytoskeleton is fully disintegrated (right column), affecting the elastic properties of the cells. See the article by Titushkin and Cho on page 3693.