The Wellcome Trust — a London-based medical research charity — has just announced the winners of its 2012 image competition, and they are positively stunning. Take the scanning electron micrograph featured above, for example. Can you guess the subject of the photograph? It may be the most widely consumed psychoactive drug on Earth, but it looks awfully unfamiliar at this level of detail.

Figure it out? They're caffeine crystals, jumbled together into structures that measure just 40 microns in length. (As a point of reference, 1 millimeter = 1,000 microns). Captured by Annie Cavanaugh and David McCarthy, it's just one of this year's 16 winning images. We've featured a handful of this year's best below, but you can check out the rest (via a cool, interactive image gallery) at The Wellcome Image Awards.

All captions via Wellcome Trust

Chicken embryo vascular system
Vincent Pasque / University of Cambridge
This fluorescence micrograph shows the vascular system of a developing chicken embryo (Gallus gallus), two days after fertilisation. Injecting fluorescent dextran revealed the entire vasculature used by the embryo to feed itself from the rich underlying yolk inside the egg. At this stage of development, the embryo and its surrounding vasculature are a little smaller than a 5p coin.

Moth fly (Psychodidae)
Kevin MacKenzie / University of Aberdeen
This false-coloured scanning electron micrograph shows a moth fly (Psychodidae), also known as a drain fly. As its name suggests, the fly's larvae commonly live and grow in domestic drains; the adult fly emerges near sinks, baths and lavatories. The moth flies' bodies and wings are covered in hairs, which gives them a 'fuzzy', moth-like appearance. The fly is 4-5 mm long, and each eye is approximately 100 microns wide.

Diatom frustule
Anne Weston / London Research Institute
This false-coloured scanning electron micrograph shows a diatom frustule. Diatoms are unicellular organisms and a major group of algae. Diatoms are encased within a hard cell wall made from silica. Frustules have a variety of patterns, pores, spines and ridges, which are used to determine genera and species. Diatoms are one of the most common types of phytoplankton, and their communities are often used to measure environmental conditions such as water quality. This diatom is approximately 80 microns in diameter.

Microneedle vaccine
Peter Demuth
This scanning electron micrograph shows an array of 'microneedles' made from a biodegradable polymer. Researchers have shown these materials can be used to deliver vaccines and therapeutics to the outer layers of the skin in a safe and painless way. Each microneedle is approximately 700 microns high and 250 microns wide at the base and can be applied to the skin as a one centimetre-squared patch.

Cell division
Kuan-Chung Su and Mark Petronczki / London Research Institute
This composite confocal micrograph uses time-lapse microscopy to show a cancer cell (HeLa) undergoing cell division (mitosis). The DNA is shown in red, and the cell membrane is shown in cyan. The round cell in the centre has a diameter of 20 microns.

Intracranial recording for epilepsy
Robert Ludlow / UCL Institue of Neurology
This photograph shows the surface (cortex) of a human brain belonging to an epileptic patient. The image displays the bright red arteries that supply the brain with nutrients and oxygen and the purple veins that remove deoxygenated blood. This photograph was taken before an intracranial electrode recording procedure for epilepsy, in which electrical activity is measured from the exposed surface of the brain.