Bells

The bell is a percussion instrument and an idiophone. Many types of bells exist.

String quartet

A string quartet consists of four string players, it appeared in the late 18th century.

The countries of the Americas

Learning about the geographic location, capitals and flags of American countries through exercises in three levels of difficulty.

Piano

The piano is one of the most popular instruments in the world. It is a chordophone which produces sounds mechanically.

Legendary ancient empires

Numerous legendary empires were built (and destroyed) in the course of history.

Relief map of China

An introduction to the relief and hydrography of China.

Legendary medieval empires

Numerous legendary empires were built (and destroyed) in the course of history.

Horse mill

Machines powered by animals were mainly used in mills, for grinding grains.

Arctic tern

The Arctic tern is famous for its long migration route: it flies from the Arctic to the Antarctic and back again each year.

How does it work? - LCD screens

A liquid-crystal display utilises the light modulating properties of liquid crystals.

How does it work? - Plasma display television

This animation explains how a plasma display television works.

How does it work? - CRT television

This animation demonstrates how a CRT television works.

Stegosaurus

A type of prehistoric reptile having bony plates on its back, which aided thermoregulation.

Dentition of mammals

The dentition of different species of mammals reflect their feeding habits.

Levels of biological organization below the individual

Levels of biological organization from the level of the individual organism to the level of cells.

Mesopotamian inventions (3rd millennium BC)

These tools, revolutionary even in their simplicity, are still in use today.

How does it work? - Cell phone

This animation demonstrates how cell phones work.

Wankel engine

A type of rotary engine of high efficiency

Archaeopteryx

The archaeopteryx shows characteristics of both birds and reptiles. It is probably the ancestor of birds.

Southern plantation with slaves (USA, 19th century)

Before the American Civil war the use of slaves on plantations was typical in the Southern states.

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