This article discusses the hypothesis that ultralight scalars, specifically fuzzy dark matter (FDM), could serve as the dark matter in the universe. FDM is a very light boson with a de Broglie wavelength of about 1 kpc, which is much larger than typical scales in galaxies. The authors argue that FDM could explain some discrepancies in the predictions of the standard cold dark matter (CDM) model on galactic scales, such as the lack of observed dark matter halos in certain mass ranges and the absence of dark matter density cusps in galaxy centers. The paper reviews the particle physics motivations for FDM, including its potential to arise from axion-like fields with approximate shift symmetries. It also explores the astrophysical consequences of FDM, such as the formation of soliton-like cores in dark matter halos, the relaxation processes in FDM systems, and the potential effects on galaxy structures like stellar disks, bulges, and binary stars. The authors analyze how FDM could influence the dynamics of galaxies, including the possible disruption of star clusters, thickening of galactic disks, and the orbital decay of supermassive black holes. The study also addresses the observational implications of FDM, noting that it could provide a better fit to certain observations than CDM, particularly in the context of high-redshift galaxies and the late reionization observed by the Planck satellite. However, there is tension with observations of the Lyman-α forest, which suggest a higher mass for FDM. The authors conclude that FDM is a viable alternative to CDM, particularly for explaining certain galactic-scale phenomena, and that further observational tests are needed to confirm its validity.This article discusses the hypothesis that ultralight scalars, specifically fuzzy dark matter (FDM), could serve as the dark matter in the universe. FDM is a very light boson with a de Broglie wavelength of about 1 kpc, which is much larger than typical scales in galaxies. The authors argue that FDM could explain some discrepancies in the predictions of the standard cold dark matter (CDM) model on galactic scales, such as the lack of observed dark matter halos in certain mass ranges and the absence of dark matter density cusps in galaxy centers. The paper reviews the particle physics motivations for FDM, including its potential to arise from axion-like fields with approximate shift symmetries. It also explores the astrophysical consequences of FDM, such as the formation of soliton-like cores in dark matter halos, the relaxation processes in FDM systems, and the potential effects on galaxy structures like stellar disks, bulges, and binary stars. The authors analyze how FDM could influence the dynamics of galaxies, including the possible disruption of star clusters, thickening of galactic disks, and the orbital decay of supermassive black holes. The study also addresses the observational implications of FDM, noting that it could provide a better fit to certain observations than CDM, particularly in the context of high-redshift galaxies and the late reionization observed by the Planck satellite. However, there is tension with observations of the Lyman-α forest, which suggest a higher mass for FDM. The authors conclude that FDM is a viable alternative to CDM, particularly for explaining certain galactic-scale phenomena, and that further observational tests are needed to confirm its validity.