Rosella is a pH-sensitive fluorescent biosensor that was recently deposited with Addgene by Dr. Mark Prescott. This system was developed for monitoring and analyzing autophagy of cytosol and organelles in yeast cells. Autophagy (Greek for “self-eating”) is induced by a lack of nutrients and targets cytosol and organelles to the vacuole/lysosome for degradation and recycling. The key to Rosella’s autophagy-sensing abilities is that its fluorescence emission spectra changes when it goes from a more neutral pH compartment, like the cytosol, to the higher pH of the vacuole. Read on to learn more about prior methods for studying autophagy and how Rosella improves upon them.