In the fourth public debate session of the course How to set up a citizen laboratory and build collaboration networks, we will see three initiatives organized during the months of confinement to encourage the creation of projects that dealt with the problems derived from the pandemic. These are three experiences from which many lessons can be learned since they have tried various collaboration formats: Frena la curva (Rosa Castizo), Hackathon vence al virus (Juan Jiménez Morillas) y Reactiva Madrid (Ángel Niño).