A study published in *Nature* (2008) identifies a small set of warmth-activated neurons (AC neurons) in the *Drosophila* brain that control temperature preference. These neurons express the ion channel dTRPA1, which functions as a molecular sensor of warmth. Flies with normal dTRPA1 function select temperatures around 25°C, their optimal growth temperature, while those with reduced or eliminated dTRPA1 function prefer warmer temperatures. The AC neurons help avoid slightly elevated temperatures and work with a distinct cold-avoidance pathway to set the fly’s preferred temperature. This internal thermal sensing pathway allows flies to select a narrow temperature range optimal for survival. The study also shows that dTRPA1 is expressed in three types of neurons in the *Drosophila* brain: LC, VC, and AC neurons. AC neurons, located in the anterior brain, are warmth-activated and express dTRPA1. When exposed to increasing temperatures, AC neurons show increased calcium activity, indicating warmth responsiveness. dTRPA1 knockdown in AC neurons disrupts warmth avoidance, suggesting that AC neurons are essential for normal thermal preference behavior. The study further demonstrates that dTRPA1 is involved in thermosensation and that its expression in AC neurons is sufficient to restore normal thermal preference. The findings challenge the previous view that *Drosophila* sense moderate warming using thermosensors in the third antennal segment. Instead, the study shows that internal thermosensors, such as AC neurons, are involved in temperature preference. The study also shows that dTRPA1 is a molecular sensor of warming in *Drosophila* and that its misexpression can be used as a genetically encoded tool for cell-specific, inducible neuronal activation. The findings suggest that dTRPA1 may be useful in tissues like the fly brain where thermal stimulation is easier to deliver than chemical or optical stimulation. The study also shows that dTRPA1 is present in other insect species, such as the malaria mosquito *Anopheles gambiae*, and that these TRPA1s may be potential targets for disrupting thermal preference and other thermosensory behaviors in agricultural pests and disease vectors. The study highlights the importance of internal thermosensors in regulating body temperature and suggests that similar mechanisms may exist in mammals. The findings have implications for understanding how animals detect and respond to environmental temperature variation, which is critical for understanding how organisms survive in and adapt to a dynamic climate.A study published in *Nature* (2008) identifies a small set of warmth-activated neurons (AC neurons) in the *Drosophila* brain that control temperature preference. These neurons express the ion channel dTRPA1, which functions as a molecular sensor of warmth. Flies with normal dTRPA1 function select temperatures around 25°C, their optimal growth temperature, while those with reduced or eliminated dTRPA1 function prefer warmer temperatures. The AC neurons help avoid slightly elevated temperatures and work with a distinct cold-avoidance pathway to set the fly’s preferred temperature. This internal thermal sensing pathway allows flies to select a narrow temperature range optimal for survival. The study also shows that dTRPA1 is expressed in three types of neurons in the *Drosophila* brain: LC, VC, and AC neurons. AC neurons, located in the anterior brain, are warmth-activated and express dTRPA1. When exposed to increasing temperatures, AC neurons show increased calcium activity, indicating warmth responsiveness. dTRPA1 knockdown in AC neurons disrupts warmth avoidance, suggesting that AC neurons are essential for normal thermal preference behavior. The study further demonstrates that dTRPA1 is involved in thermosensation and that its expression in AC neurons is sufficient to restore normal thermal preference. The findings challenge the previous view that *Drosophila* sense moderate warming using thermosensors in the third antennal segment. Instead, the study shows that internal thermosensors, such as AC neurons, are involved in temperature preference. The study also shows that dTRPA1 is a molecular sensor of warming in *Drosophila* and that its misexpression can be used as a genetically encoded tool for cell-specific, inducible neuronal activation. The findings suggest that dTRPA1 may be useful in tissues like the fly brain where thermal stimulation is easier to deliver than chemical or optical stimulation. The study also shows that dTRPA1 is present in other insect species, such as the malaria mosquito *Anopheles gambiae*, and that these TRPA1s may be potential targets for disrupting thermal preference and other thermosensory behaviors in agricultural pests and disease vectors. The study highlights the importance of internal thermosensors in regulating body temperature and suggests that similar mechanisms may exist in mammals. The findings have implications for understanding how animals detect and respond to environmental temperature variation, which is critical for understanding how organisms survive in and adapt to a dynamic climate.