Feedback from the first stars and galaxies and its influence on structure formation

Once the first sources have formed, their mass deposition, energy injection and emitted radiation can deeply affect the subsequent galaxy formation process and influence the evolution of the IGM via a number of so-called feedback effects. The word 'feedback' is by far one of the most used in modern cosmology, where it is applied to a vast range of situations and astrophysical objects. Generally speaking, the concept of feedback invokes a back reaction of a process on itself or on the causes that have produced it. The character of feedback can be either negative or positive. Here, I will review the present status of investigation of the feedback effects from the first stars and galaxies.