Recent results from JWST and the Atacama Large Millimeter-submillimeter Array (ALMA) have shown that the first galaxies in the Universe began forming within 500 Myr after the Big Bang. This means that over 13 billion years have passed since the first appearance of luminous objects. The past few decades in astronomy have outlined the general process by which modern galaxies like our Milky Way evolved from primordial structures - dark matter coalesced into halos where normal matter formed stars and galaxies, which then merged to create more massive structures. However, much of the detail still remains elusive - why, how, and when did primordial galaxies make their transformation into their modern counterparts? What were the conditions like within and without these galaxies that led them to evolve in this specific way? Which of the objects we observe in the distant Universe, i.e., in our distant past, were the ancestors of modern objects, including spiral galaxies like our Milky Way, dwarf galaxies, globular clusters, quiescent and elliptical galaxies, and the supermassive black holes at the centres of galaxies? Which of them played the biggest role in the major events in the history of our Universe such as reionisation? Are there objects that we have yet to discover that might completely change our understanding of how galaxies evolved? The aim of this thesis is to attempt to answer these questions. I begin with an overview of our current understanding of the timeline and physics of galaxy evolution, along with relevant observational techniques and their limitations. I then present our study of the physics of an early galaxy at 𝑧 ∼ 7.13 (∼ 800 million years after the Big Bang). Using emission from the metalenriched gas in the far-infrared, specifically from the [C ii] 158μm, [N ii] 122μm, [O iii] 52 and 88μm lines, along with the underlying continuum emission from the dust, I estimate the metallicity, strength of ionisation, and gas density in the inter-stellar medium (ISM) of this galaxy. This analysis, the first of its kind at 𝑧 > 7, provides a rare glimpse into the ISM of an early galaxy, and provides constraints on when it may have formed. By extension, this provides a timeline for the formation of the first galaxies in the Universe, and their dust and gas properties. Next, I analyse the internal structure of ∼ 50 star-forming galaxies between cosmic noon and reionisation (𝑧 ∼ 4–6). I once again use the [C ii] 158μm line and emission from the dust continuum, along with the emission in the ultraviolet (UV) and optical. I estimate the centroids of these four emissions and their offsets relative to each other, and find that around ∼ 25% of the galaxies in the study display significant offsets. As the [C ii] emission arises from the gas in the galaxy, continuum from the dust, and UV and optical emission directly from stars, an offset between the emissions implies an offset between the gas, dust, and stars in the galaxies, which reveals the conditions within the ISM such as the strength of feedback from stellar radiation, the distribution of dust across the galaxies, and also the general morphological structure of galaxies in this epoch. Later, I investigate the nature of an enigmatic object at 𝑧 ∼ 4.53. The spectrum includes features from a star-forming galaxy, and also from a supermassive black hole i.e., an active galactic nucleus (AGN). This object seems to be one among a growing list of a new class of objects called little red dots that were unknown prior to JWST. While a galaxy with an AGN is nothing new, pre-JWST observations used to show either a star-formation dominated or an AGN-dominated galaxy. These objects, however, seem to be caught exactly in between these two phases, which means that we may be witnessing the earliest stages of supermassive black hole formation, i.e., the progenitors of the AGN in the local Universe. Finally, I discuss the implications of these findings in the larger astronomical context, and suggest future prospects of expanding the studies to gain an even more detailed understanding of galaxy evolution.