This book demonstrates the research on VLC based indoor localization in four aspects: first, it constructs the concept and model of the system; second, positioning algorithms, as the main issue in indoor localization, are detailed; third, many approaches are proposed to further improve the positioning performance; fourth, challenges will be detailed. Impulse response with multipath reflections are analyzed. Orthogonal frequency division multiplexing (OFDM) is proposed, and positioning performance is largely improved compared to On-off-keying (OOK) modulation. The readers will get a broad view of VLC based indoor localization from the background to the future challenges.