Tissue temperature in the interscapular BAT and the skeletal muscle was recorded using the type T thermocouple probes and recorded by using the TC-2000 Meter (Sable Systems International), according to our protocol3 (link). Core body temperature was monitored using a TH-5 thermometer (Physitemp) by recording the rectal temperature of the mice. For core-body temperature recording experiment in Fig. 5i, both control (Ppargflox/flox) and PpargMyoD KO (Myod-CreERT2;Ppargflox/flox) mice were pre-treated with β-blocker and tamoxifen at room temperature for 5 days and acclimated to 15°C for additional 5 days. Wild-type mice did not receive pre-β-blocker-treatment. Subsequently, all the mice were acutely treated with β-blocker and exposed to 10°C.