The smallest creature in the house can deserve the most careful preparation.

Small animals are easy to underestimate precisely because they take up so little room. A fish, a hamster, a bird, an insect: the smaller the creature, the narrower its tolerances usually are, and the faster a wrong temperature or the wrong food becomes serious. Ease of housing gets mistaken for ease of care.

If a small animal lives with you, check one specific requirement you have been assuming rather than confirming. If one is arriving, do the reading before it comes rather than after. Their margin for error is smaller than yours.