Health education 1 Show the picture and tell pupils that this is what makes them better when they have an infection. Do they know what pneumonia is? Explain what is happening; that pneumonia is inflammation of the lungs; that the macrophage is “swallowing up” the infection, cleaning up a poorly lung. How do we keep healthy? Talk about the importance of the white cells in the blood for “cleaning up the body” - thereare about 300 million red cells in one drop of blood but fewer than half a million white cells. Discuss diet, exercise, sleep, avoiding things that make you ill in the first place.

Science 2 Take a convex lens. See how it makes things bigger. Try two lenses. What happens? Explain that the electron microscope allows huge magnifications, and how an electron gun bombards the object being studied with a stream of electrons which are then scattered when they hit the atoms of the object.

Writing 3 Write (a) an account of what the macrophage is doing in scientific language; (b) about how you feel when you see this “miracle” at work in your body. For those with a strong stomach only, write a story, inspired by the picture, called “The Alien”.

Ted Wragg is professor of education at Exeter University