The second component of building your pet's personal universe is to create a sun-of sorts. Reptiles depend on the air temperature to maintain their body heat. Room temperature is too cold for most reptiles, so you'll need to warm the cage environment as well as provide hot spots for basking (see Your Own Personal Sun). Most temperate (as opposed to desert or tropical) reptiles will appreciate air that's 75 to 80 degrees Farenheit, and the only way to be sure you are providing adequate heat is to use a thermometer-preferably of the digital, indoor/outdoor, minimum/maximum type.