The article describes the evolution of a monomeric red fluorescent protein (mRFP1) from the tetrameric red fluorescent protein (DsRed) found in Discosoma coral. The authors used a combination of targeted and random mutagenesis to disrupt the dimer interfaces of DsRed, leading to the creation of a monomeric form. This process involved eight generations of directed evolution, resulting in mRFP1, which is a monomer, matures rapidly, and has minimal emission when excited at wavelengths optimal for green fluorescent protein (GFP). mRFP1 is suitable for constructing fusion proteins and multicolor labeling in combination with GFP, as demonstrated by its functionality and trafficking in mammalian cells. However, mRFP1 has lower quantum yield and extinction coefficient compared to other DsRed variants, and it photobleaches more easily. The authors suggest that further improvements in mRFP1's properties may be achieved through additional evolutionary strategies.The article describes the evolution of a monomeric red fluorescent protein (mRFP1) from the tetrameric red fluorescent protein (DsRed) found in Discosoma coral. The authors used a combination of targeted and random mutagenesis to disrupt the dimer interfaces of DsRed, leading to the creation of a monomeric form. This process involved eight generations of directed evolution, resulting in mRFP1, which is a monomer, matures rapidly, and has minimal emission when excited at wavelengths optimal for green fluorescent protein (GFP). mRFP1 is suitable for constructing fusion proteins and multicolor labeling in combination with GFP, as demonstrated by its functionality and trafficking in mammalian cells. However, mRFP1 has lower quantum yield and extinction coefficient compared to other DsRed variants, and it photobleaches more easily. The authors suggest that further improvements in mRFP1's properties may be achieved through additional evolutionary strategies.