Practise the Russian alphabet, build words from letters.
Quetzalcoatlus was one of the largest known flying animals of all time.
Oil tankers appeared in the late 19th century; today they are among the largest ships.
Wind, as an external force, plays an important role in shaping coastal areas and steppes.
These special dolmens located in present-day Netherlands were built about 5,000 years ago.
Surface tension is the property of a liquid that allows it to obtain the smallest surface area possible.
Waterfalls form where a river flows over a steep precipice in its course.
Structures consisting of enormous stone blocks, dating back thousands of years, are monuments of megalithic cultures.
The Hussites mastered the use of war wagons in the 15th century.
A regular square pyramid is a right pyramid with a square base and four triangular faces.
This 3D introduces a centipede species widespread in the Mediterranean.
Let's learn about the bear species that became the symbol of species conservation.
Lasers are devices designed to emit narrow, monochromatic, high-intensity beams of light.
This scene presents the provinces and provincial capitals of the Netherlands.
Today called Dubrovnik, this Croatian city is known for its spectacular architecture and beautiful location.
Many of the most important food crops we consume belong to the family of nightshades.
Butyric acid (or butanoic acid) is a saturated monocarboxylic acid.
Terephthalic acid is an aromatic dicarboxylic acid.
In the disciplines dealing with the human body, it is extremely important to precisely specify the planes, axes and directions.
Organs that detect signals of the environment or of the body and transmit them to the brain as nerve impulses.
An important archaeological site located on the right bank of the Danube in eastern Serbia, within the Iron Gates gorge.
Bulgaria's natural resources include a great variety of minerals.