The universe is transitioning from rapid, violent mergers to slow, secular evolution. While mergers dominate early galaxy evolution, secular processes, involving collective phenomena like bars, oval disks, and triaxial dark halos, will shape galaxy structure in the far future. This paper focuses on secular evolution in disk galaxies, particularly the formation of pseudobulges—dense central components resembling classical bulges but formed slowly from disk gas. Pseudobulges retain characteristics of disks, such as flatter shapes, ordered velocities, and spiral structure, and are found in barred and oval galaxies. Observations and simulations support their formation, with gas accumulating in rings and central concentrations, leading to star formation. Pseudobulges are distinct from merger-built bulges, as they show disk-like features and are embedded in secular evolution. Their formation timescales are plausible, with gas densities and star formation rates indicating a few billion years for development. Secular evolution involves more than stellar aging, with bars and oval disks driving gas redistribution and star formation. This process is central to galaxy evolution, complementing hierarchical clustering and merging. Pseudobulges are common in intermediate-type galaxies and can be found in S0 and Sa galaxies. Observations and simulations show that bars and oval disks drive gas inflow, leading to rings and central concentrations. Infrared observations reveal that many "unbarred" galaxies have hidden bars, indicating that secular evolution is widespread. Nonaxisymmetric potentials, such as those from bars and oval disks, rearrange disk gas, leading to similar secular evolution in unbarred galaxies. Pseudobulges are formed through this process, with gas accumulating in rings and central regions, leading to star formation. The results highlight the importance of secular evolution in shaping galaxy structure and the formation of pseudobulges.The universe is transitioning from rapid, violent mergers to slow, secular evolution. While mergers dominate early galaxy evolution, secular processes, involving collective phenomena like bars, oval disks, and triaxial dark halos, will shape galaxy structure in the far future. This paper focuses on secular evolution in disk galaxies, particularly the formation of pseudobulges—dense central components resembling classical bulges but formed slowly from disk gas. Pseudobulges retain characteristics of disks, such as flatter shapes, ordered velocities, and spiral structure, and are found in barred and oval galaxies. Observations and simulations support their formation, with gas accumulating in rings and central concentrations, leading to star formation. Pseudobulges are distinct from merger-built bulges, as they show disk-like features and are embedded in secular evolution. Their formation timescales are plausible, with gas densities and star formation rates indicating a few billion years for development. Secular evolution involves more than stellar aging, with bars and oval disks driving gas redistribution and star formation. This process is central to galaxy evolution, complementing hierarchical clustering and merging. Pseudobulges are common in intermediate-type galaxies and can be found in S0 and Sa galaxies. Observations and simulations show that bars and oval disks drive gas inflow, leading to rings and central concentrations. Infrared observations reveal that many "unbarred" galaxies have hidden bars, indicating that secular evolution is widespread. Nonaxisymmetric potentials, such as those from bars and oval disks, rearrange disk gas, leading to similar secular evolution in unbarred galaxies. Pseudobulges are formed through this process, with gas accumulating in rings and central regions, leading to star formation. The results highlight the importance of secular evolution in shaping galaxy structure and the formation of pseudobulges.