The Nikon Small World contest highlights the best microscope images taken each year.

The 2019 contest attracted more than 2,000 entries from nearly 100 countries.

This year's top image is a picture of a turtle embryo awash with a rainbow of fluorescent colors.

Other winners include a cross-section of a tulip bud, the eye of a housefly, and a jewel bearing.

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Human eyes may be remarkable tools to view the universe, but they also restrict our perception of reality to a limited, macroscopic slice.

Fortunately, microscopes grant us access to a fantastic, beautiful, and sometimes shocking universe that hides beyond the limits of vision.

To honor the mastery required to capture the microscopic world and appreciate its wonders, the Nikon Small World contest picks the best photographs taken through a microscope — and has done so each year for decades.

"Our goal has always been to show the world how art and science intersect," Eric Flem, Nikon Instruments' communications manager, said in a press release. "As new imaging and microscopy techniques develop over the years, our winners showcase these technology advances more and more creatively."

For the 45th year of the contest, four judges reviewed more than 2,000 pictures submitted from nearly 100 countries. A little more than 100 photos stood out from the pack.

We've posted the top 20 below — including images of a fluorescent turtle embryo, a close-up of a housefly's compound eye, and a psychedelic cross-section of a tulip flower bud (above) — along with 20 of our other favorites from the contest.