Intracellular organelles are essential for cellular architecture and function, and their size regulation is critical for maintaining cellular homeostasis. Organelle size often scales with cell size, governed by mechanisms that integrate resource allocation, stochastic dynamics, and feedback controls. Here we review these underlying biophysical principles of organelle size control, including the limiting pool hypothesis, stochastic assembly processes, and feedback-driven growth dynamics. We discuss how negative feedback motifs stabilize size, while positive feedback can amplify growth and maintain size under specific conditions. Additionally, we discuss recent advances in modeling size control for organelles with nucleation and fission-fusion dynamics. By integrating experimental observations with theoretical insights, this review provides a conceptual understanding of the design principles governing organelle size regulation in dynamic cellular environments.