Flow splitter for splitting a primary fluid flow into a plurality of secondary fluid flows for performing experiments, which flow splitter comprises: - a manifold, which manifold has a manifold inlet for receiving the primary fluid flow, and a plurality of manifold outlets for releasing the plurality of secondary fluid flows, - a plurality of capillary units, each of the capillary units comprising: - a unit inlet for receiving a secondary fluid flow from a manifold outlet, - a unit outlet for releasing said secondary fluid flow, - a capillary, which capillary is arranged between the unit inlet and the unit outlet such that said secondary fluid flow passes through the capillary, - a heater and/or a cooler for adjusting the temperature of the capillary and therewith influencing the flow rate of the secondary fluid flow passing through said capillary, - a housing for accommodating at least the capillary and heater and/or cooler of said capillary unit, which housing provides thermal insulation of the capillary, - a flow sensor for measuring the flow rate of the secondary fluid flow through the capillary unit, which flow sensor can be arranged either inside or outside the housing, - a flow adjustment unit for adjusting the flow rates of the secondary fluid flows, which flow adjustment unit comprises a temperature control device for individually controlling the heater and/or cooler of each capillary unit in response to the flow rate that is measured by the flow sensor of that capillary unit, wherein the capillary in the housing of each capillary unit has been prepared beforehand and the resistance to fluid flow of the capillary at a reference temperature and with a fluid of a known viscosity has been measured and is known; and wherein the capillary units are exchangeable. - a manifold, which manifold has a manifold inlet for receiving the primary fluid flow, and a plurality of manifold outlets for releasing the plurality of secondary fluid flows, - a plurality of capillary units, each of the capillary units comprising: - a unit inlet for receiving a secondary fluid flow from a manifold outlet, - a unit outlet for releasing said secondary fluid flow, - a capillary, which capillary is arranged between the unit inlet and the unit outlet such that said secondary fluid flow passes through the capillary, - a heater and/or a cooler for adjusting the temperature of the capillary and therewith influencing the flow rate of the secondary fluid flow passing through said capillary, - a housing for accommodating at least the capillary and heater and/or cooler of said capillary unit, which housing provides thermal insulation of the capillary, - a flow sensor for measuring the flow rate of the secondary fluid flow through the capillary unit, which flow sensor can be arranged either inside or outside the housing, - a unit inlet for receiving a secondary fluid flow from a manifold outlet, - a unit outlet for releasing said secondary fluid flow, - a capillary, which capillary is arranged between the unit inlet and the unit outlet such that said secondary fluid flow passes through the capillary, - a heater and/or a cooler for adjusting the temperature of the capillary and therewith influencing the flow rate of the secondary fluid flow passing through said capillary, - a housing for accommodating at least the capillary and heater and/or cooler of said capillary unit, which housing provides thermal insulation of the capillary, - a flow sensor for measuring the flow rate of the secondary fluid flow through the capillary unit, which flow sensor can be arranged either inside or outside the housing, - a flow adjustment unit for adjusting the flow rates of the secondary fluid flows, which flow adjustment unit comprises a temperature control device for individually controlling the heater and/or cooler of each capillary unit in response to the flow rate that is measured by the flow sensor of that capillary unit, wherein the capillary in the housing of each capillary unit has been prepared beforehand and the resistance to fluid flow of the capillary at a reference temperature and with a fluid of a known viscosity has been measured and is known; and wherein the capillary units are exchangeable.