These colourful and intricate images are this year's Wellcome Image Awards finalists. From a greenfly's eye, to a curved human spine - they showcase the best in science imaging techniques.

Below is the final selection of 20 - but which one will be named overall winner on Wednesday 18 March?

Scroll through the varied selection below - and click to hear the fascinating stories behind four of the images.

Video narration by the head of Wellcome Images, Catherine Draycott.

Media playback is unsupported on your device Media caption Wellcome Images 2015

This purplish chap below is a boll weevil - found on the front porch of a suburban house.

It is a pest beetle that feeds on - and lays its eggs in - the cotton plant.

The scanning electron microscope composite was taken by Daniel Kariko, who is based in the United States.

Shaped like a golf ball, this image below is in fact a scanning electron micrograph of a greenfly's eye - created by Kevin Mackenzie from the University of Aberdeen.

The eye is made up of thousands of repeating units known as ommatidia, each with a tiny lens on the front surface.

Each lens faces a slightly different direction, and together they produce a mosaic image.

This allows the fly to see very quick movements - but not fine details or objects that are far away.

The next long photograph from Mark Bartley, based at Addenbrookes Hospital in Cambridge, is of a 79-year-old woman's back, showing an abnormally curved spine.

This hunched back appearance is known as kyphosis, or "dowager's hump", and causes the upper back and shoulders to round forward.

These rainbow colours reveal nerve cells in a cross-section of an adult mouse brain.

It is a confocal micrograph created by Luis de la Torre-Ubieta, based at the University of California in Los Angeles, US.

Featuring an intricate pattern, with an almost carpet-like appearance in places, this photo is of a stomach chamber in a goat.

It shows the goat's reticulum - the second of four stomach chambers found in cattle, sheep and goats.

The oesophagus - the tube that carries food from the mouth to the stomach - is seen at the top of the image.

The photo by Michael Frank is of a specimen now held at the Royal Veterinary College in London, that would have come from a culled animal.

It is not a work of abstract modern art - but instead a colourful representation of a fruit-fly's nervous system.

Transmission electron micrographs were used to create a digital colour-coded map of the area, showing cells called neurones that carry messages and responses through an organism.

It was created by Albert Cardona, based at the Howard Hughes Medical Institute's Janelia Research Campus in Virginia, US.

The next image is a colour-coded map of part of a mouse kidney as it breaks down food to make energy.

The colours show chemical reactions.

The image was a team effort - created by five people who have worked across the United States - Jefferson R Brown, Robert E Marc, Bryan W Jones, Glen Prusky and Nazia Alam.

These blue tree-like branches spread out from a Purkinje cell, or neuron, found in the brain of a rat.

It is a scanning electron micrograph created by Prof M Hausser, Sarah Rieubland and Arnd Roth - based at UCL in London.

The Tuatara of New Zealand are all that remain of a group of animals that used to share the Earth with dinosaurs.

Their name comes from the spines along their neck, back and tail - Tuatara is a Maori word meaning "spiny back".

This is a micro-computed tomography (micro-CT) scan of the skull and front legs of one specimen - created by Sophie Regnault, who is studying at the Royal Veterinary College in London.

The next image is of mouse lungs, in blue and green - with microparticles in pink.

The microparticles are being studied to see if they can deliver medicine to the lungs, and which could, in time, help improve cancer treatments in humans.

The image was created by Gregory Szeto, Adelaide Tovar and Jeffrey Wyckoff, at MIT in the US.

Similarly here, this is scanning electron micrograph of a single brain cell, with a rectangular hole cut in it.

It is so scientists can study how tiny, nanometre-sized particles - in red and brown - interact with the surface, to see if they might be good carriers of medicines that could treat tumours.

The image was created by Khuloud T Al-Jamal, Serene Tay and Michael Cicirko.

Maurizio De Angelis's next image is reminiscent of something from science fiction.

It is an illustration of pollen grains being released from a flower in the Asteraceae family.

This sepia-toned image has been created in the style of the 19th Century drawings of the French neurologist Joseph Jules Dejerine.

Made by Flavio Dell'Acqua, based at King's College London, it shows bundles of nerve fibres inside a healthy adult living human brain.

The roundish cell in the right of this next image is under attack by the pointier natural killer (NK) cell on the left.

It looks like the NK cell - which looks for signs of disease as part of the immune system - is taking a giant bite.

It will release toxic chemicals - shown in red - that will cause the second cell to self-destruct.

The super-resolution micrograph was created by N Dieckmann and N Lawrence at the University of Cambridge.

Geraldine Thompson took this next photo of an interactive multi-sensory unit, which is used to distract and comfort anxious children receiving treatment in hospital.

The image shows equipment in use at the Royal Manchester Children's Hospital.

No wonder this old anatomy model looks sleepy - he was at the end of his working life when he was found in Dublin.

Photographer Anthony Edwards snapped the specimen as it was about to be thrown out with rubbish - to honour the service it had provided to medical students at the city's Trinity College.

And if you have not done it yet - click the video at the top of the article to see the last four of the finalists close up.

Images in the video created by David Linstead, Andrew Polaszek, Michael Frank, Dave Farnham. All images subject to copyright.

All the images will go on display at the Wellcome Trust HQ in London, before going on tour to 11 science centres, museums and galleries across the UK and parts of the US.