In a method of moving droplets, local heat is applied to a surface portion of a droplet for an amount of time sufficient to create a Marangoni flow in the droplet. Droplets are suspended in an emulsion in a carrier liquid on a substrate. A laser beam is used to move one of the droplets. the droplet consists of a first substance and a carrier liquid consists of a second substance that is not mixable with the first substance. The droplet is placed in the carrier liquid, and the mixture is emulsified. The emulsified mixture is placed on a substrate. Then the local heat is applied to the surface of the droplet. The first substance may include oil and the second substance may include water.