MACROPHAGE AND BACTERIUM 2,000,000X // Macrophages circulate through the blood, searching for bacterial infection. When bacteria are found, macrophages engulf and digest them.

RED BLOOD CELL // A portion of a red blood cell is shown in this illustration, with the cell membrane at the top, and lots of hemoglobin (red) at the bottom.

BASEMENT MEMBRANE // This illustration shows a portion of basement membrane, a structure that forms the support between tissues in your body.

MUSCLE // Part of a muscle sarcomere is shown here, with actin filaments in blue and myosin filaments in red. The long yellow proteins are the huge protein titin.

NUCLEUS // This view shows DNA being replicated in the nucleus. DNA polymerase is shown at the center in purple, with a DNA strand entering from the bottom and exiting as two strands towards the top.