The authors investigate the electronic properties of a vertical quantum dot containing a tunable number of electrons, ranging from zero to over 40. They observe Coulomb oscillations in the current-voltage characteristics, which reveal a shell structure in the addition energy required to add electrons to the dot. This shell structure is attributed to the complete filling of shells for specific electron numbers, such as 2, 6, and 12, which are considered "magic numbers" in a two-dimensional harmonic potential. The shell structure persists as long as the lateral potential is radially parabolic and the confinement energy is comparable to or larger than the interaction energy. When a magnetic field is applied, the current peaks shift in pairs due to the filling of spin-degenerate single-particle states. However, at sufficiently small magnetic fields (B < 0.4 T), the pairing behavior is modified by Hund's rule, favoring the filling of parallel spins. This is evident in the evolution of the current peaks, where the pairing rearranges to align with Hund's rule. The authors also observe intriguing pairing behaviors at higher temperatures, suggesting further investigation into these phenomena. The study provides insights into the atom-like properties of artificial atoms in quantum dots, highlighting the importance of both Coulomb interactions and magnetic fields in determining the electronic structure.The authors investigate the electronic properties of a vertical quantum dot containing a tunable number of electrons, ranging from zero to over 40. They observe Coulomb oscillations in the current-voltage characteristics, which reveal a shell structure in the addition energy required to add electrons to the dot. This shell structure is attributed to the complete filling of shells for specific electron numbers, such as 2, 6, and 12, which are considered "magic numbers" in a two-dimensional harmonic potential. The shell structure persists as long as the lateral potential is radially parabolic and the confinement energy is comparable to or larger than the interaction energy. When a magnetic field is applied, the current peaks shift in pairs due to the filling of spin-degenerate single-particle states. However, at sufficiently small magnetic fields (B < 0.4 T), the pairing behavior is modified by Hund's rule, favoring the filling of parallel spins. This is evident in the evolution of the current peaks, where the pairing rearranges to align with Hund's rule. The authors also observe intriguing pairing behaviors at higher temperatures, suggesting further investigation into these phenomena. The study provides insights into the atom-like properties of artificial atoms in quantum dots, highlighting the importance of both Coulomb interactions and magnetic fields in determining the electronic structure.