Flavin-based fluorescent proteins: emerging paradigms in biological imaging

- Flavin-based fluorescent proteins (FbFPs) enable low-oxygen imaging unlike GFP.
- FbFPs are smaller than GFP, which makes them superior as robust tags for viruses.
- FbFPs can be used for optogenetic protein inactivation via singlet oxygen production.
- FbFPs have been engineered to develop bright, photostable, and thermostable variants.
- We highlight key challenges and suggest new directions to maximize potential of FbFPs.