Pyrene can be used as a fluorescent probe for various industrial purposes. For example, it can be included in photocurable or thermally curable compositions and monitoring the fluorescence emission spectra before and after some curing will provide an indication of how much curing has occurred. Such monitoring can be carried out multiple times during a manufacturing process. Monitoring can also be done at different locations of a composition such as at inner and outer surfaces of a photocured or thermally cured layer.