The article by W.D. Heiss discusses the nature and significance of exceptional points (EPs) in various physical problems, including classical and quantum mechanics. EPs are points where eigenvalues coincide, leading to a reduction of the problem to a two-dimensional matrix. These points are associated with symmetry breaking in $\mathcal{PT}$-symmetric Hamiltonians, where numerous experiments have been conducted, particularly in optics and atomic/molecular physics. EPs play a crucial role in quantum phase transitions, quantum chaos, multichannel scattering, and nuclear physics, where they can cause dramatic effects such as resonance narrowing and laser oscillation. The article also explores the physical manifestations of EPs in microwave cavities, $\mathcal{PT}$-symmetric Hamiltonians, atomic/molecular physics, laser physics, and open systems. Additionally, it discusses the impact of EPs on approximation schemes and their role in classical systems and fluid mechanics. The summary highlights the widespread occurrence of EPs and their significant effects on observables in various physical phenomena.The article by W.D. Heiss discusses the nature and significance of exceptional points (EPs) in various physical problems, including classical and quantum mechanics. EPs are points where eigenvalues coincide, leading to a reduction of the problem to a two-dimensional matrix. These points are associated with symmetry breaking in $\mathcal{PT}$-symmetric Hamiltonians, where numerous experiments have been conducted, particularly in optics and atomic/molecular physics. EPs play a crucial role in quantum phase transitions, quantum chaos, multichannel scattering, and nuclear physics, where they can cause dramatic effects such as resonance narrowing and laser oscillation. The article also explores the physical manifestations of EPs in microwave cavities, $\mathcal{PT}$-symmetric Hamiltonians, atomic/molecular physics, laser physics, and open systems. Additionally, it discusses the impact of EPs on approximation schemes and their role in classical systems and fluid mechanics. The summary highlights the widespread occurrence of EPs and their significant effects on observables in various physical phenomena.