This animation demonstrates the main sources of air pollution: agriculture, industry and urban settlements.
This animation demonstrates the structure and most important peripherals of desktop computers.
Careful tooth brushing is an important part of oral hygiene.
The ‘upright man’ used tools and could set fire.
The ruler of the vast Mongol Empire was the Khan.
The pericarp of real fruits develops from the carpel, while the pericarp of pseudofruits develops from other parts of flowers.
Ports must provide necessary infrastructure and services for industry and marine transport.
The most important weapons of medieval Arab warriors were the bow and the sword.
Honeybees produce a sweet and nutritious substance, honey.
An ant colony consist of a queen, male ants and workers.
Igloos were the typical dwellings built by Eskimos living in the Arctic zone.
The water supply system provides clean and safe drinking water for the consumers.
The diameter of our galaxy is about 100,000 light years; it contains more than 100 billion stars, one of which is our Sun.
The Byzantine Emperor was the head of the Byzantine Empire, the direct continuation of the Roman Empire.
The Aztec Empire was a despotic, militaristic state ruled by the tlatoani.
Chlorophyll is a photosensitive green pigment found in plants; it absorbs light energy, thus plays a vital role in photosynthesis.
The knee joint is made up by the femur, the tibia and the kneecap.
The migration of large human populations began in Ancient times.
NAD⁺ is a coenzyme that plays an important role mainly in catabolic processes, while NADP is important in anabolic processes as hydrogen carriers.
Airports provide infrastructure and services necessary for aviation.