World´s Smallest...The African Pygmy Mouse

Adults weigh 3 - 12 grams (0.11 to 0.42 oz)  measure between 30-80 mm in lenght (1.2 to 3.1 inches) + the tail which can be 20 - 40 mm (0.79 to 1.6 in) long...

It lives 2-4 years and are active both during the day and at night. 

In the wild they gather pebbles in front of its burrow and in the morning they drink the dew deposit on them overnight...