The needle-free injector, which is specially designed for children, is used for hypodermic injection, e.g., insulin and growth hormone injection. Compared with needle injector, it eliminates children's fear of needles, while minimizing such piercing pain and probability of cross infection. Moreover, it improves the bio-availability of drug, so its response time is reduced, while the localized hardening of soft tissue caused by prolonged use of local injections can be avoided. The design inspired by the jigsaw?puzzles, which creates a modular structure. The extraordinary softness of body is conveyed by its round shapes. Its bright colors, like a trick, let the children forget the pain.