In contemporary observational astronomy, the synergy of powerful telescopes probing the entire electromagnetic spectrum is pivotal for uncovering the true nature of celestial objects. This seminar explores the distinctive characteristics of two cosmic realms using this synergistic approach: the enigmatic small, faint star-forming galaxies that may have played a pivotal role in reionizing the universe, and the colossal, quiescent galaxies that puzzlingly appeared only a few hundred million years after the Big Bang. In the first part of the talk, I will present the results of a 60-hour multi-band ALMA observation of a normal, main-sequence, sub-L* galaxy at z=6. We sample the dust continuum emission with 9 bands and constrain the molecular gas content and obscured star formation rate via CO J=1,7, CI, [CII], and dust for 2 lensed images (magnification~20). The lensing effect allows probing luminosity and mass regimes up to 100 times lower than previously explored. Complementing ALMA with resolved photometry and spectroscopy with JWST/NIRCam+NIRSpec provides key properties such as gas-phase metallicity. With these observations, I will address critical physical processes, such as how efficiently gas turns into stars and how rapidly metals and dust accumulate in low-luminosity galaxies, influencing their abilities to disperse ionizing photons in their surroundings. In the second half of the talk, we fast-forward to the end of the galaxy life cycle. I will present recent results on the large number of massive, quiescent galaxies that JWST now allows us to find at z>4. I will introduce a simple and effective color diagram to identify these systems even recently after their main quenching epoch, demonstrating its application to purely public data and highlighting the importance and preciousness of archives.