The 2021 Sagan Summer Workshop will focus on young planets and the circumstellar disks from which they form during the first few million years of a star's lifetime. As a protoplanet accretes material from the disk, dynamical interactions drive migration and produce disk substructures such as the gaps, rings and spirals now detected in high-resolution optical, near-infrared, and submillimeter images. Over the next 100 million years, planetary systems continue to evolve through processes such as collisions, differentiation, and scattering. These late-epoch evolutionary processes are reflected in the structure and distribution of secondary dust disks. These debris disks, formed as the result of planetesimals stirring, serve as signposts for the presence of planetary systems.