In this activity, learners investigate the touch sensory system and discover how to plan and carry out their own experiments. In "CLASS EXPERIMENT," learners find that the ability to tell that two points rather than just one are pressing on the skin depends on two things: the density of skin sensory receptors and the connections that the sensory nerve cells make in the brain. They learn basic facts about sensory receptors and nerve connections, and use their estimates of receptor density to predict the size of the brain areas devoted to input from different skin regions. In "TRY YOUR OWN EXPERIMENT," learners design their own experiments, investigating, for example, how touch information is important in motor tasks, or whether additional sensory input can interfere with two-point discrimination. This lesson plan includes background information and guides for educators and learners. Note: total learning time may be reduced if the number of skin areas tested are limited and you restrict the materials in the second part of the activity.