This book begins with a very simple everyday observation, the movement of the sun in the sky. As the observations are repeated from different locations, at different times of the day and year and with more and more accuracy, a very complex picture emerges. Unexpectedly, all the complexity can be explained using very simple ideas. This is the essence of science. Many areas are covered in this small book, from planetary movement and chemistry to biology and climate change. It has been specifically written for young children. It is not however a collection of facts. Many areas of science can be descriptively understood using a few very elementary ideas of fundamental physics. The aim here is to make the readers understand the interrelationships between the various areas and the strength of fundamental physics with the minimum of scientific terms and no mathematics at all. But as one moves from the movement of planets to living beings and climate, only an approximate explanation is possible. The book explains "how well" we understand, which is very important as the description of some popular unscientific ideas made from time to time shows.