Method of releasing one or more droplets of a first fluid (F1) with one or more droplets of a second fluid (F2) within a microfluidic apparatus wherein the method comprises - providing a main channel carrying one or more droplets of the second fluid (F2) immersed in a carrier fluid (FC), - providing an auxiliary channel , formed as a reservoir having a predefined closed volume and comprising the first fluid, fluidly coupled to the main channel at two intersections (T1, T2), with a first intersection (T1) via a first orifice configured to create a first fluid interface between the carrier fluid and the first fluid in the auxiliary channel, and with a second intersection (T2) downstream to the first intersection (T1) via a second orifice configured to create a second fluid interface between the carrier fluid and the first fluid, - imparting a flow of the carrier fluid (FC) into the main channel , inducing therefrom a difference of pressure between the first and second orifice generating a balance condition such that a meniscus of the second fluid interface is maintained in the auxiliary channel , at the vicinity of the second orifice, - creating a balance deviation, with regard to the balance condition, greater than a predefined threshold, thereby triggering a release of a volume of the first fluid (F1) from the second fluid interface into the main channel , wherein the balance deviation with regard the balance condition at the second fluid interface is generated by: - at least one droplet of the second fluid (F2) passing in the main channel between the first intersection and the second intersection, thereby increasing the pressure drop and triggering a release of a volume of the first fluid (F1) from the second fluid interface , and/or - an actuator allowing a release of a volume of the first fluid (F1) from the second fluid interface . - providing a main channel carrying one or more droplets of the second fluid (F2) immersed in a carrier fluid (FC), - providing an auxiliary channel , formed as a reservoir having a predefined closed volume and comprising the first fluid, fluidly coupled to the main channel at two intersections (T1, T2), with a first intersection (T1) via a first orifice configured to create a first fluid interface between the carrier fluid and the first fluid in the auxiliary channel, and with a second intersection (T2) downstream to the first intersection (T1) via a second orifice configured to create a second fluid interface between the carrier fluid and the first fluid, - imparting a flow of the carrier fluid (FC) into the main channel , inducing therefrom a difference of pressure between the first and second orifice generating a balance condition such that a meniscus of the second fluid interface is maintained in the auxiliary channel , at the vicinity of the second orifice, - creating a balance deviation, with regard to the balance condition, greater than a predefined threshold, thereby triggering a release of a volume of the first fluid (F1) from the second fluid interface into the main channel , - at least one droplet of the second fluid (F2) passing in the main channel between the first intersection and the second intersection, thereby increasing the pressure drop and triggering a release of a volume of the first fluid (F1) from the second fluid interface , and/or - an actuator allowing a release of a volume of the first fluid (F1) from the second fluid interface . <EOS>