I started my astronomy career in Tenerife, where I did a PhD in Astrophysics at the Instituto de Astrofisica de Canarias. During that time I studied how the most massive galaxies in the Universe form and evolve. They hold the majority of luminous matter of the Universe, and thus are a key piece of the puzzle of the formation of the Universe. Later, I moved to the Big Island of Hawaii, working as postdoctoral researcher at the Subaru Telescope. During the 3 years there, I glimpsed how hard it is to make such big telescopes to work while digging further into the mysteries of massive galaxies. I then moved to Melbourne, Australia, as a postdoctoral researcher at Swinburne University. During the past 2 years I switched my interest onto the small, less massive galaxies, considered to be the primordial building blocks that created the big, massive ones at later times. Only by understanding how these ancient galaxies formed we can solve the mystery of the larger ones. However, there is an entire Universe that was being hidden at plain sight, full of small, very diffuse and dim galaxies. These are now finally accessible with the latest technology developed in the large optical telescopes, using state-of-the-art techniques to analyze them. With the project I will carry as a Junior Leader Fellow, I aim to reveal the main properties of these new types of galaxies and the role they play into the big puzzle of galaxy formation and evolution, and ultimately, our place into the Universe