Optical interactions with matter involve energy exchange and momentum exchange. The momentum aspect gives rise to strong optical forces that can be used to manipulate and control the positions and velocities of atoms and particles. I will review the basic physics of this field and will discuss our experiments to trap particles using a strongly focused laser beam in an optical tweezers trap. By trapping particles that produce fluorescent light dependent on the ion concentration in a liquid, we are working to create a new technique for measuring chemical properties inside cells. We are also using holographic optical tweezers to trap multiple particles and perform in situ multiplexed spectroscopy. New experiments and potential applications will be discussed.