Thirty years ago, the first planet around another Sun-like star was detected by astrophysicists at the University of Geneva. This discovery marked the dawn of exoplanet research with the ultimate goal of finding life anywhere other than Earth and understanding our Solar System and its place in the Universe in that process. More than six thousand exoplanets have been discovered since then, and many instruments have been built to characterize their size, mass, and atmosphere. What scientists found was a variety of unique worlds, with types of planets not seen in our Solar System. One of the most successful methods for detecting these exoplanets, the transit method, uses the planet occulting the surface of its host star, reducing the amount of light received from the star, depending on the stellar and planetary radii. Transits can also access the atmosphere of the exoplanet through spectrographs, which scatter light at different wavelengths: the planet will appear larger at the signature wave- lengths absorbed by the chemical species that make up the atmosphere. This technique is called transmission spectroscopy. Different wavelength ranges give access to various chemical components: atomic species such as sodium, calcium, and lithium absorb generally more in the visible bandpass with singular lines, and molecular species such as water, carbon dioxide, and methane absorb more in the infrared through large bands. This thesis focuses on atmospheric characterization of exoplanets using high-resolution transmission spectroscopy (HRTS), with transit observations from current state-of-the-art ground-based facilities. Each chapter introduces a different type of planet and discusses the modern context of the technique and its complementarity with recent research from space-based observatories, notably the early results of JWST. Most categories of exoplanets and their modern population trends are explored: hot Jupiters, Neptune-sized planets, and the smaller sub-Neptunes and super-Earths. All these studied exoplanets and their context within different population trends are explored in this thesis, with some of the highest precision and sensitivity reachable today. As exo-atmospheric research evolves rapidly and with new facilities coming in the next few years, the astrophysics community will be able to solve those peculiar planetary trends through chemical (non-)detections statistics over a large sample of planets, thanks to improved instruments, and as the number of exoplanets known grows at a faster rate than ever. These answers will bring us closer to understanding our own Solar System and to the atmospheric characterization of Earth-sized planets.