<p>The fundamental role of magnetic materials in modern science and technology has driven a rapid surge in research on unconventional magnetism in recent years. Among these systems, altermagnets, which simultaneously exhibit zero net magnetization in real space and anisotropic spin splitting in momentum space, have garnered particular interest for both fundamental physics and technological applications. RuO₂ stands as the pioneering and most extensively studied candidate in this class. While the intrinsic magnetic order of RuO₂ remains a subject of active debate, numerous exotic phenomena characteristic of altermagnetism have been observed experimentally. In this review, we explore various facets of the altermagnetism through specific case studies in RuO₂, including its crystal and magnetic structures, electronic band properties, and transport phenomena. We critically assess the debate surrounding the intrinsic magnetism in RuO₂, incorporating evidence from altermagnetic signatures in transport with contrasting results from magnetic and spectroscopic measurements. Finally, we discuss possible future research directions on this topic.</p>