Gas giant
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope.
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.