Substances in a solid state are generally speaking denser than inner liquid state. But water is an exception. The density of ice is lower than that of water . if it was the other way around, the ice would sink on the bottom thus destroying the water – inhabitants .

In contrast to animals and bacteria, plants lead a tethered lifestyle. They cannot go off in search of a better lot. Therefore, they have learnt how to solve problems on the spot and how to adapt constant changes including the winter and endure unfavorable conditions.

From the first antibiotics to the growth of stem cells; from observing micro-organisms to the testing of new medicines all of this job is possible thanks to the petri Dish, a short, flat cylinder covered with a transparent lid of a corresponding shape.

It is believed that the wheel was created in Mesopotamia no later than 6000years ago. Not long ago however, evidence appeared that suggested that the wheel existed in Europe as early as 7000 years ago. At that time wheels where solid massive and mostly made from boards. They were fastened to a rectangular wooden body to produce a cart that one could harness onto onagers and bulls. Such carts were of great value and were used only by combat and to transport nobility.