Today, we can communicate with voice and video calls, and organize online conferences. But, we are not able to do that with smells. Even though we know all the olfactory receptors and detailed anatomy of the olfactory circuits, we still do not know the computational basis of olfaction. The puzzle could be broken down into the following questions: how the diverse olfactory receptors encode odor molecules; how the olfactory codes are transformed in the brain. We study these questions using the fruit fly larvae, which have a minimal conserved olfactory system. Combining microfluidics and calcium imaging, we recorded all the olfactory sensory neurons’ responses to broad odorant stimuli. We discovered important features in the code, on the one hand, could separate odor intensity and identity; on the other hand, indicate the fundamental properties of the molecular recognition process in olfaction. Based on these results, we developed a setup to manipulate the larval olfactory code on-demand, which could facilitate the further investigation of the transformation of the olfactory code in the larval brain.