2. Guide children to observe and compare fingerprints.

3. Discuss the shape of fingerprints. The shapes of fingerprints include: arrow-shaped water waves, eddies, etc. Tell children that everyone's fingerprints are different. People in the world don't have an identical fingerprint, and everyone's fingerprint won't change for life, so it can be used to identify people.

4. It is found that fingerprints will be left in touched places, and fingerprints will also be left in places that we can't see with the naked eye, leaving many sweat holes. Sweat secreted by sweat glands will reach our hands through sweat pores, and the sweat on fingers will leave fingerprints when it touches objects.

5. Guide children to tell the purpose of fingerprints: don't underestimate fingerprints, it is very useful! Fingerprints are made up of many small particles arranged on the skin. These small particles are very sensitive. As long as you touch an object with your hand, you will immediately report all kinds of "information" such as cold, hot, soft and hard to the brain headquarters. Then the brain gives orders and directs actions according to these "information".