A directed evolution approach was used to produce mApple and several other red fluorescent protein variants belonging to the "mFruit" series. Compared to mStrawberry, mApple is significantly more photostable, in addition to exhibiting excellent brightness and rapid maturation. The peak excitation and emission wavelengths of mApple are 568 and 592, respectively. The cytoskeletal network was targeted in the fox lung cells featured in the digital video sequences in this section with mApple fused to alpha-actinin. In addition, the cytoskeleton was labeled with a chimera of mEmerald and Lifeact, resulting in some visible overlap of the fluorescent markers.