A method including: a) providing a first well with a first layer of a first flowable material and a second layer of a second flowable material, and a second well with a first layer of a first flowable material different from the first flowable material of the first well, b) locating the flowable material inlet within the first layer, c) sampling a first volume of the first flowable material, d) displacing the flowable material inlet relative to the first well to locate the flowable material inlet within the second layer, e) sampling a second volume of the second flowable material, f) displacing the flowable material inlet relative to the first and second wells to locate the flowable material inlet within the first layer of the second well, and g) sampling or dispensing into the second well a third volume of the first flowable material of the second well.