Two-color imaging with Sapphire/EGFP. Shown in the upper row of panels are HeLa cells that have been transfected with plasmids for expression of both Sapphire-actin and EGFP-NLS. Shown in the lower row of panels are identically treated HeLa cells expressing Sapphire-actin and mWasabi-NLS. Owing to the residual excitation of EGFP at 400 nm, the nucleus fluoresces brightly in the Sapphire emission channel in the top row of panels. In contrast, mWasabi is not significantly excited at 400 nm and thus the nucleus is much dimmer than the actin filaments in the bottom row of panels. Scale bars represent 10 μm.