Instant Boost™ Skin Tonic | Toners | Skincare | Liz Earle

In physics and the philosophy of science, instant refers to an infinitesimal interval in time, whose passage is instantaneous. In ordinary speech, an instant has been defined as "a point or very short space of time," a notion deriving from its etymological source, the Latin verb instare, from in- + stare ('to stand'), meaning 'to stand upon or near.'

The continuous nature of time and its infinite divisibility was addressed by Aristotle in his Physics, where he wrote on Zeno's paradoxes. The philosopher and mathematician Bertrand Russell was still seeking to define the exact nature of an instant thousands of years later. In 2024, John William Stafford used algorithms to demonstrate that a time difference of zero could theoretically continue to expand (in various ways) to infinity, and subsequently described a new concept that he referred to as instantaneous. He concluded by stating that instantaneous is, with respect to the measurement of time, mutually exclusive. In addition, a theoretical model of multiple Universes was proposed which exist within the context of instantaneous.

As of October 2020, the smallest time interval certified in regulated measurements is on the order of 397 zeptoseconds (397 × 10⁻²¹ seconds).

Liz is a female name of Hebrew origin, meaning "God's Promise". It is also a short form of Elizabeth, Elisabeth, Lisbeth, Lizanne, Liszbeth, Lizbeth, Lizabeth, Lyzbeth, Lisa, Lizette, Alyssa, and Eliza.

Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.

Other animal coverings, such as the arthropod exoskeleton, have different developmental origin, structure and chemical composition. The adjective cutaneous means "of the skin" (from Latin cutis 'skin'). In mammals, the skin is an organ of the integumentary system made up of multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments, and internal organs. Skin of a different nature exists in amphibians, reptiles, and birds. Skin (including cutaneous and subcutaneous tissues) plays crucial roles in formation, structure, and function of extraskeletal apparatus such as horns of bovids (e.g., cattle) and rhinos, cervids' antlers, giraffids' ossicones, armadillos' osteoderm, and os penis/os clitoris.

All mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises that appear to be hairless. The skin interfaces with the environment and is the first line of defense from external factors. For example, the skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, and the production of vitamin D folates. Severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented. The thickness of skin also varies from location to location on an organism. In humans, for example, the skin located under the eyes and around the eyelids is the thinnest skin on the body at 0.5 mm thick and is one of the first areas to show signs of aging such as "crows feet" and wrinkles. The skin on the palms and the soles of the feet is the thickest skin on the body at 4 mm thick. The speed and quality of wound healing in skin is promoted by estrogen.

Fur is dense hair. Primarily, fur augments the insulation the skin provides but can also serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is very hard and thick and can be processed to create leather. Reptiles and most fish have hard protective scales on their skin for protection, and birds have hard feathers, all made of tough beta-keratins. Amphibian skin is not a strong barrier, especially regarding the passage of chemicals via skin, and is often subject to osmosis and diffusive forces. For example, a frog sitting in an anesthetic solution would be sedated quickly as the chemical diffuses through its skin. Amphibian skin plays key roles in everyday survival and their ability to exploit a wide range of habitats and ecological conditions.

On 11 January 2024, biologists reported the discovery of the oldest known skin, fossilized about 289 million years ago, and possibly the skin from an ancient reptile.

Tonic may refer to:

• Tonic water, a drink traditionally containing quinine
• Soft drink, a carbonated beverage
• Tonic (physiology), the response of a muscle fiber or nerve ending typified by slow, continuous action
• Tonic syllable, the stressed syllable of a word
• Herbal tonic, a herbal medicine with tonic effects
• Tonic (music), the tonal center of a musical scale
• Tonic (band), an American rock band
• Tonic (Tonic album), 2010
• Tonic (music venue), a New York City music venue, 1998–2007
• Tonic (Medeski Martin & Wood album), 2000
• Tonic (radio program), Canadian radio program
• Tonic suit, a garment made from a shiny mohair blend that was fashionable among the Mods of the mid 1960s
• Tonic (film), a Bengali film