The invention relates to a method for mixing a first stream of droplets (1) with at least one second stream of droplets (2) to obtain a third stream of fused droplets (3), by collision and fusion of at least one droplet of the first stream (1) with at least one droplet of the second stream (2). The first stream of droplets (1) and the at least one second stream of droplets (2) are generated in a synchronized manner. The invention also relates to a device for generating and mixing a first stream of droplets (1) and at least one second stream of droplets (2) to obtain a third stream of fused droplets (3), to a droplet, a plurality of droplets, or to a two-dimensional or three-dimensional scaffold generated by this method. Through the described method and device, it is possible to exploit the soformed fused droplets for several different applications such as 3D patterning (a), high throughput screening (b) and combinatorial studies (c).