Smallest organisms
With a mass of approximately and a length of 5 centimetres (2.0 in), the bee hummingbird ("Mellisuga helenae") is the world's smallest bird species and the smallest warm-blooded vertebrate. Called the "zunzún" in its native habitat on Cuba, it is lighter than a Canadian or U.S. penny. It is said that it is "more apt to be mistaken for a bee than a bird". The bee hummingbird eats half its total body mass and drinks eight times its total body mass each day. Its nest is 3 cm across.
Least weasel
The least weasel ("Mustela nivalis"), common weasel, or simply weasel in the UK and much of the world, is the smallest member of the genus "Mustela," family Mustelidae and order Carnivora. It is native to Eurasia, North America and North Africa, and has been introduced to New Zealand, Australia, Malta, Crete, Bermuda, Madeira Island, the Azores, the Canary Islands, São Tomé, the Falkland Islands, Argentina and Chile. It is classified as least concern by the IUCN, due to its wide distribution and large population throughout the Northern Hemisphere.