We are delighted to present a collection of six papers in this special section of the Journal of Biomedical Optics on the use of photonics and nanotechnology in biophysics and biomedical research. Three of these papers are related to the use of optical nanomaterials for imaging and phototherapeutic applications. Specifically, Bahmani et al. investigated the effect of polyethylene glycol (PEG) coating on the resulting uptake of optical polymeric nanocapsules by human spleen macrophages in vitro. The investigators report that PEGylation delays the uptake of these nanocapsules by at least six hours, providing a potentially effective strategy to increase the circulation time of these nanocapsules for in vivo imaging and phototherapeutic applications.