Targeted transfection of nanoparticles carrying a Cy3-labelled microRNA (Cy3-miR) into human fetal cardiac fibroblast cells. Image shows Rab5 positive (green) early endosomes; LAMP1 positive (grey) lysosomes and transfected Cy3-miR (red), confirming that these Cy3-miR-carrying nanoparticles are absent in either the early endosome or lysosome, but present in late endosome.