The expansion in global cellphone network coverage coupled with advances in cellphone imaging capabilities present an opportunity for the advancement of cellphone microscopy as a low-cost alternative to conventional microscopy for disease detection in resource-limited regions. The development of cellphone microscopy has also benefitted from the availability of low-cost miniature microscope components such as low-power light-emitting diodes and ball lenses. As a result, researchers are developing hardware and software techniques that would enable such microscopes to produce high-resolution, diagnostic-quality images. This approach may lead to more widespread delivery of diagnostic services in resource-limited areas where there is a shortage of the skilled labour required for conventional microscopy and where prevalence of infectious and other diseases is still high. In this paper, we review current techniques, clinical applications and challenges faced in the field of cellphone microscopy.