Planet
The smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon.
Smallest organisms
Frogs include the smallest vertebrates known. The smallest known frog species is "Paedophryne amauensis", with a snout-vent length reported as 7.7 mm, which occurs among leaf-litter in the tropical montane forests of New Guinea. Other very small frogs include "Brachycephalus didactylus" from Brazil (reported as 9.6-9.8 mm), several species of "Eleutherodactylus" such as "Eleutherodactylus iberia" (around 10mm) and "Eleutherodactylus limbatus" (8.5–12 mm) and "Eleutherodactylus orientalis" (12.5 mm) from Cuba, Gardiner's Frog "Sechellophryne gardineri" from the Seychelles (up to 11 mm), several species of "Stumpffia" such as "Stumpffia tridactyla"(8.6–12  mm) and "Stumpffia pygmaea"(10–12.5 mm；females:11 mm) and "Wakea madinika"(males:11–13 mm；females:mm 15–16 mm) from Madagascar. "Paedophryne swiftorum"(Body length 8.5 mm) is not included in the smallest vertebrates known with other nine species of frogs. The two species "Microhyla borneensis"(males:10.6–13 mm；females:16–19 mm) and "Arthroleptella rugosa"(males:11.9–14.1 mm；females:15.5mm) were once the smallest known frogs from the Old World. In general these extremely small frogs occur in tropical forest and montane environments. There is relatively little data on size variation among individuals, growth from metamorphosis to adulthood or size variation among populations in these species. Additional studies and the discovery of further minute frog species are likely to change the rank order of this list.