The invention provides exemplary systems and methods for processing solid supports. According to one system, a probe is provided having a distal end and a lumen terminating at the distal end. The transport mechanism is adapted to place the distal end of the probe into a well having a plurality of solid supports that are held within a fluid. A detection mechanism is provided to detect the presence or absence of one of the solid supports at the distal end while the distal end is within the fluid. A measuring system is provided to measure the general size of the attached solid support.