A new instrument is presented for investigating interactions between individual colloidal particles, emulsion droplets, foam bubbles, and other particle-particle or particle-surface interactions. Measurement capabilities are demonstrated by measuring interfacial tension, coalescence time for emulsion droplets, adhesion between giant multilamellar vesicles, and adhesion between model food emulsion particles. The magnitude of the interaction force that can be measured or imposed, ranges from 1 nN to 1 mN for particles ranging in size from 10 mu m to 1 mm in diameter.