Taken together, the active droplets consist of a mixture of long and short PSS. During the droplets' short lifetimes, the long PSS forms mature domains as speckles within the droplets. As the fuel depletes, the activated peptide population decreases, preferentially expelling the short PSS. The speckles are expelled from the mother droplet in its final minutes. The offspring speckles move independently in the reaction solution until they finally dissolve. With our mechanistic insights, we tested which parameters affect the droplet division. Given our interest in using these droplets for the de novo synthesis of life, we focussed on tuning the offspring's lifetime and number. To quantify the division, we used continuously imaged microfluidic reactors because, in such reactors, only one large droplet is produced, facilitating the quantification of the selfdivision process. Using the abovementioned conditions, microreactors were produced by combining peptide, PSS, and fuel in a buffered aqueous solution. Immediately after mixing, 5 µL of this aqueous solution was transferred to 50 µL of fluorinated oil and mixed gently. The resulting emulsion comprised millions of polydisperse water droplets ranging from tens to hundreds of microns in diameter-the microreactors. Within these microreactors, we observed the formation of coacervate-based droplets. We imaged the entire reactor in X, Y, and Z with time intervals of roughly 10 seconds until all the droplets had dissolved (Fig. ). Early in the cycle, we observed multiple coacervate droplets that rapidly grew and sank to the bottom of the reactor, where they fused until only one droplet remained. We chose to image with a diameter of roughly 35 µm such that the volume of the final droplet was similar from reactor to reactor at roughly 460 µm 3 (Fig. ). In line with the bulk microscopy data, after roughly 17 minutes, the division process started and produced tens of offspring droplets (Fig. , supporting movie 1). To quantify the division process, we projected all Z-planes of one microreactor to one plane (Fig. ). In the Z-plane projection, we observed the formation of vacuoles, the formation of speckles, and, a few seconds later, the liberation of the speckles as droplet fragments from which we conclude the droplets in the confined space of a microreactor behave similarly to those in bulk. We wrote a Python script that counts the droplets in each frame of the confocal videos (See SI), which revealed the number of droplets rapidly decreased to one because of the fusion. After 17 minutes, the number of droplets increased from one (the "mother") to an average of 12 (the "offspring") before rapidly decreasing when all offspring dissolved.