There is provided a method and/or system which allow on-chip preconditioning of complex real-world samples and/or handling of limited amounts of target material, and/or on-chip nucleic acid amplification process, using a free droplet containing magnetic attractable material. The nucleic acid amplification process comprises controlling the position of the magnetic attractable material and performing the nucleic acid amplification in a thermocycling droplet located onto at least one temperature zone. The low thermal masses of the herein described heaters/temperature sensors come along with fast temperature transitions within the corresponding temperature zones allowing impressing temperature gradients in at least one temperature zone between subsequent or within the same thermocycle(s). Additionally, the variable residence times of the droplet in a given temperature zone permit to customize the denaturation, annealing and/or extension times within the same or between different PCR runs. Additionally, the herein described method and/or system allow amplification of one or more nucleic acid molecules. Additionally, the herein described method and/or system allow real-time monitoring with or without the presence of magnetic attractable material bound to said nucleic acid molecule.