When the first rays of sunlight in the morning pass through the gaps in the curtains, you feel a slight itch at your feet, because the cat is tiptoeing through the folds of your pajamas; when you open the door, the furry head has already bumped into your palm, and the dog is wagging its tail and circling in the entrance hall, shaking off joy in every inch of air. These uninvited warmth are the most precious gifts that pets give to humans.