Fundamental ideas that help to understand the way of thinking and feeling of the little ones. Child psychology is a fascinating field of research and intervention, as well as being one of the most important. Knowing better or worse the way of behaving, thinking and feeling of the little ones can have very important implications in their physical and mental development. Not surprisingly, childhood is a stage in which we are especially sensitive to what happens around us, and if we do not have the knowledge or proper supervision parents and guardians should be aware that there may be severe consequences.For this reason, in the following lines, we will see a selection of fundamental ideas belonging to the world of child psychology, with which it is possible to better understand children.