An apparatus and system for contacting a mobile elongate solid phase, e.g. a ribbon with a flowing fluid phase, and a method for using the same in, for example solid phase synthesis. A particular apparatus comprises (i) a conduit which is of circular or non-circular transverse cross section and which defines a lumen to contain both the flowing fluid phase and the mobile elongate solid phase; (ii) fluid phase ports in communication with the lumen to allow the fluid phase to enter the lumen, flow through it and exit it; and (iii) solid phase ports in communication with the lumen to allow the mobile solid phase to enter the lumen, move through it and exit it, the apparatus being adapted to prevent fluid egress from its interior through the solid phase ports.Also provided is a continuous process for synthesising and screening molecules, comprising passing an elongate solid phase through successive treatment stations where different stages of a solid phase synthesis are performed, and screening the synthesised molecules for activity.