Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 11 days development, showing beating heart and blood flowing over gills, Ecuador. Endangered. (non-ex)

Nigel Cattlin / Immature caterpillar of a codling moth (Cydia pomonell) eating its way through a gallery in a ripening apple fruit, Berkshire, July

Morley Read / Developing embryo of the Ecuadorian monkey frog (Phyllomedusa ecuatoriana), showing heart beating and blood flowing, Morona Santiago Province, Ecuador, (non-ex)

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle) internal detail. Misool, Raja Ampat, West Papua, Indonesia.

Stephen Dalton / Two Water Fleas (Daphnia sp.), showing transparency of bodies and internal organs. UK, September.

Pete Oxford / Northern Glassfrog (Hyalinobatrachium fleischmanni) underside showing internal organs, northwest Ecuador

Graham Eaton / An underwater view of a mountain stream showing internal reflections on the water surface, Snowdonia NP, Gwynedd, Wales, UK, December 2009.

Juergen Freund / X-ray of the shell of the Pearly / Chambered nautilus {Nautilus pompilius} showing the internal chambers of the shell.

Nigel Cattlin / Doyenne du Comice pear (Pyrus communis) fruit with deformity and internal hard growth caused by Pear stony pit virus, cross section. Berkshire, England, UK. October.

Nigel Cattlin / Doyenne du Comice pear (Pyrus communis) fruit with deformity and internal hard growth caused by Pear stony pit virus, cross section. Berkshire, England, UK. October.

Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 11 days development, showing beating heart and blood flowing over gills, Ecuador. Endangered. (non-ex)

Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 11 days development, showing beating heart and blood flowing over gills, Ecuador. Endangered. (non-ex)

Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 10 days development, showing beating heart and blood flowing over gills, Ecuador. Endangered. (non-ex)

Tony Wu / Sperm whale (Physeter macrocephalus) nostril. This species have a single blowhole on the left side of their heads. The other nostril has been modified into an internal organ called the phonic lip that...

Matthew Maran / Meat offal, including sheep hearts, for sale at butchers counter. North London, England

David Fleetham / Sea cucumber (Bohadschia argus) which has ejected a part of its internal organs called Cuvierian tubules. These significantly sticky strings are a defense mechanism designed to deter predators. Yap,...

Tony Wu / Ram's horn squid / Little post horn squid (Spirula spirula) internal shell with Pelagic goose barnacles (Lepas sp.). South Africa, Atlantic Ocean.

Lucas Bustamante / Reticulated glass frog (Hyalinobatrachium valerioi) viewed through hole in leaf seeing internal organs through its transparent skin, Canande, Esmeraldas, Ecuador.

Lucas Bustamante / Female Reticulated glass frog (Hyalinobatrachium valerioi) viewed from below seeing internal organs through transparent skin, Canande, Esmeraldas, Ecuador.

Emanuele Biggi / Cockroach (Ectobidae sp.) with transparent body so internal organs can be seen. Los Amigos Biological Station, Peru

Emanuele Biggi / Cockroach (Ectobidae sp.) with transparent body so internal organs can be seen. Los Amigos Biological Station, Peru

Steve Downer / Close-up larva of Fruit fly (Drosophila melanogaster) showing internal structure, UK

Ingo Arndt / Scientists implanting wires in the brain of a Desert locust (Schistocerca gregaria) to measure brain activity. University of Marburg, Germany. November 2013.

Ingo Arndt / Scientists implanting wires in the brain of a Desert locust (Schistocerca gregaria) to measure brain activity. University of Marburg, Germany. November 2013.

Paul D Stewart / Skeleton of a seahorse (Hippocampus sp.) showing the remarkable structure of bones that form a virtual exoskeleton, with few deep internal bones, in this unusual vertebrate group.

Paul D Stewart / Calcite belemnite fossils, the calcite internal structures of prehistoric squid like species. These have been shattered by a meteorite impact, 14.5 million years ago, they were already over 100 millio...

Paul D Stewart / Calcite belemnite fossils, the calcite internal structures of prehistoric squid like species. These have been shattered by a meteorite impact, 14.5 million years ago, they were already over 100 millio...

Paul D Stewart / Calcite belemnite fossils, the calcite internal structures of prehistoric squid like species. These have been shattered by a meteorite impact, 14.5 million years ago, they were already over 100 millio...

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Mark MacEwen / Bornean orangutan (Pongo pygmaeus) female portrait, Tanjung Puting reserve, Camp Leakey, Central Kalimantan, Borneo.

Juan Manuel Borrero / Illustration of internal Nautilus anatomy. Pencil and watercolor painting.

Jan Hamrsky / Narrow-winged Damselfly (Coenagrion) nymph, translucent with some internal organs visible. Europe, August.

Klaus Echle / Developing and mature Douglas Fir (Pseudotsuga menziesii) cones, a young one split in two to show internal structure. Black Forest, Germany, August.

Pete Oxford / Opened Polybia Paper Wasp Nest showing internal structure. Cocaya River, Eastern Amazon Rain Forest, the border of Peru and Ecuador.

Juergen Freund / Green urn sea squirt / tunicate (Didemnum molle) internal detail. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Circle or C-hooks vs. traditional J-hooks of longline tuna fishing boat of Nutrindo Freshfood International, Sulawesi, Indonesia, October 2009. Changing from the classic J hook to C hooks can dramatic...

Florian Möllers / Deutsche Bahn Tower lit up by internal lights in the evening, Potsdamer Platz, Berlin, Germany. January 2009

Stephen Dalton / Water Flea (Daphnia sp.), showing transparency of body and internal organs. UK, September.

Pete Oxford / Northern Glassfrog (Hyalinobatrachium fleischmanni) underside showing internal organs, northwest Ecuador

Pete Oxford / Northern Glassfrog (Hyalinobatrachium fleischmanni) underside showing internal organs, northwest Ecuador

Graham Eaton / An underwater view of a mountain stream showing internal reflections on the water surface, Snowdonia NP, Gwynedd, Wales, UK, December 2009.

Philippe Clement / Cuttlebone, the internal shell of the Common cuttlefish (Sepia officinalis), France

Philippe Clement / Cuttlebone, the internal shell of the Common cuttlefish (Sepia officinalis), France

Thomas Marent / Northern Glassfrog (Hyalinobatrachium fleischmanni) underside showing internal organs, Colombia

Thomas Marent / Northern Glassfrog (Hyalinobatrachium fleischmanni) underside showing internal organs, Colombia

Suzi Eszterhas / Spotted Hyena {Crocuta crocuta} carrying off internal organ from carcass, Masai Mara Triangle, Kenya

Juergen Freund / X-Ray of Sea Snail Shell showing internal spiral

Juergen Freund / X-Ray of Sea Snail Shell showing internal spiral

Mark Moffett / Army Ant (Eciton burchellii) carrying leaf, about to be landed on by tiny parasitic fly which will attempt to lay an egg on the submajor, the egg will then hatch into a larva which will consume the an...

Keith Scholey / Looking up inside mature Strangler fig at internal structure when host dead (Ficus destruens) Daintree NP, Queensland, Australia

Jane Burton / Common Frog (Rana temporaria) golden-yellow morph tadpoles with their internal organs visible through their unpigmented skin

Jane Burton / Common Frog (Rana temporaria) golden-yellow morph tadpoles with their internal organs visible through their unpigmented skin

Kim Taylor / Freshwater worm {Dero} amongst pond debris

Kim Taylor / Leech {Helobdella stagnalis} showing internal structures

Kim Taylor / Leech {Herpobdella sp} showing internal structures

Pete Oxford / Underside of Glass frog {Hyalinobatrachium sp} internal organs visible. Ecuador

Heidi & Hans-Juergen Koch / Glass Frog (Cochranella antisthenesi) underside showing internal organs, native to South America

Greg Basco/ BIA / Reticulated Glass Frog (Hyalinobatrachium valerioi) translucent underside showing internal organs, Costa Rica

Solvin Zankl / Ram's horn squid (Spirula spirula) portrait. This species has an internal, chambered, endogastrically coiled shell in the shape of an open planispiral. The shell functions to control buoyancy. O...

Solvin Zankl / Ram's horn squid (Spirula spirula) portrait. This species has an internal, chambered, endogastrically coiled shell in the shape of an open planispiral. The shell functions to control buoyancy. O...

Solvin Zankl / Ram's horn squid (Spirula spirula) portrait. This species has an internal, chambered, endogastrically coiled shell in the shape of an open planispiral. The shell functions to control buoyancy. O...

Solvin Zankl / Pelagic polychaete (Alciopa reynaudii) portrait. These pelagic worms are known for their fragile, thin, transparent bodies and large, complex spherical eyes with an internal lens. Observed during RV S...

Will Watson / Park pale made up from an internal ditch and a wooden fence, beside house, Moccas Park National Nature Reserve, Herefordshire, England, UK, December 2023. Fence made from cleft Oak wood.

Will Watson / Park pale made up of internal ditch and a wooden fence, Moccas Park National Nature Reserve, Herefordshire, England, UK, December 2023. Fence made from cleft Oak wood.

Will Watson / Park pale made up of internal ditch and a wooden fence, Moccas Park National Nature Reserve, Herefordshire, England, UK, December 2023. Fence made from cleft Oak wood.

Will Watson / Sign beside gated entrance to Moccas Park National Nature Reserve, with park pale made up of internal ditch and a wooden fence, Herefordshire, England, UK, December 2023. Wooden fence made from cleft...

Tom Vierus / Surgical implant of an internal tag into a juvenile Bull shark (Carcharhinus leucas), Rewa River, Viti Levu, Fiji. December, 2018.

Emanuele Biggi / Green bright-eyed frog (Boophis viridis) adult resting on glass showing transparent underbelly. Andasibe-Mantadia National Park, Madagascar. Controlled conditions.

Lucas Bustamante / Mashpi glassfrog (Hyalinobatrachium mashpi) underside, internal organs visible. Captive, occurs in Ecuador.

Joel Sartore / Photo Ark / Yuruani glass frog (Hyalinobatrachium iaspidiense) view of underside and jumping out of frame. Captive.

Jen Guyton / Nurse Berta Barros examining baby Rosalina's heart with her mother behind. Rosalina was born during Cyclone Idai. Outskirts of Gorongosa National Park, Mozambique. April 2019.

Doug Wechsler / Green frog (Lithobates clamitans) with throat skin going up and down pumping air in and out of lungs, Philadelphia, Pennsylvania, USA. July.

Emanuele Biggi / Hydnophytum formicarum, a myrmecophile plant that live in a mutualistic association with a colony of ants. Detail of internal structures. Bako National Park, Borneo.

David Fleetham / Sea cucumber (Bohadschia argus) which has ejected a part of its internal organs called Cuvierian tubules. These significantly sticky strings are a defense mechanism designed to deter predators. Yap, M...

NaturePL Showreels / Our 2021 nature showreel showcasing a selection of our wildlife, timelapse, slow-motion and drone footage.

Philippe Clement / Cuttlebone washed ashore on sandy beach, buoyancy organ and internal shell of the European common cuttlefish (Sepia officinalis), Hauts-de-France, France, July