Tan obtained important results about the Julia and Mandelbrot sets, in particular investigating their fractality and the similarities between the two. For example she showed that at the Misiurewicz points these sets are asymptotically similar through scaling and rotation. She constructed examples of polynomials whose Julia sets are homeomorphic to the Sierpiński carpet and which are disconnected. She contributed to other areas of complex dynamics. She also wrote some surveys and popularisation work around her research topics.