In the rehydration of paraffin embedded tissues, it is important to immerse the slides in 100% ethanol after treating with xylene because xylene is immiscible with water. The slides cannot be immediately changed from xylene to the subsequent ethanol solutions containing water or else xylene may remain on the tissue section and interfere with staining. Since ethanol is miscible with both xylene and water, 100% ethanol effectively clears xylene and prepares the samples for introduction of water.