This week at Matters of Activity, we are switching methods to a more interventionist style: constituting a « fermentation club » is a participatory and collaborative way to investigate on the relation between human and microbiome. I got together that hands-on fermentation workshop with the help of my colleagues Alwin Cubasch and Anna Heitger. This is also a round of stimulating conferences with a proper panel that participants will attend from their own kitchen. I will share my kombucha routines, pieces of my kombucha cultures, and will get in conversation with the architect Bastian Beyer and the microbiologist Skander Hathroubi around cellulose building bacteria.