Abstract　 　 
Recent observations reveal that merely 3 billion years after the Big Bang a correlation between the structure and stellar populations of galaxies has already emerged. I will discuss progress towards understanding this precursor of the Hubble sequence, by deep surveys using the major observing facilities: PEP with Herschel, SINS with VLT, SEDS with Spitzer, CANDELS with HST. I will demonstrate an array of striking similarities between galaxy populations near and far, in terms of structure and mode of star formation, when viewed in relation to the so-called main sequence of star formation. Key aspects in which galaxies during the peak of cosmic star formation differ from their descendants today will be discussed as well. In addition, state-of-the-art hydrodynamical simulations coupled to radiative transfer shed light on the nature of both star-forming and quiescent galaxies in the young universe, and the connection between them.