Cell-based therapy offers a promising solution for the treatment of diseases and injuries that conventional medicines and therapies cannot cure effectively, and thus comprises an encouraging arena for future medical breakthroughs. The development of an accurate and quantitative non-invasive cell tracking technique is a highly challenging task, which could help in evaluating the effectiveness of the treatment. Moreover, cell tracking could elucidate essential knowledge regarding fundamental trafficking patterns and poorly-understood mechanisms underlying the success or failure of cell therapy. This talk will focus on gold nanoparticles (GNPs), which provide cells with `visibility` in a variety of imaging modalities for stem cell therapy, immune cell therapy and cancer treatment. Current challenges and future prospects relating to the use of GNPs in such roles are discussed.