Primary bone marrow macrophages derived from mouse plated on a coverslip and imaged live. Phase contrast microscopy allows us to see the dense f-actin rich leading edge, ruffles, mitochondria, the nucleus, and other organelles throughout the volume of the cells. At the center of the image is a polarized lamellipod of a crawling cell. The glass micropipette at the bottom of the image is delivering CSF (colony stimulating factor) locally and the cell may be responding.