Gareth Griffiths and Lasse Evensen just got accepted an article where they demonstrate how the zebrafish embryo is a nice system for monitoring nanoparticle behaviour in vivo. My contribution was to produce fluorescent liposomes, with or without PEG. The circulation time of the liposomes was greatly increased with addition of PEG. The article is published in the journal Nanoscale, and you can read more here.