Bio-molecules are principal building blocks of living species and their inter-play is the cause of bio-activities. Various sophisticated experimental techniques as well as theoretical studies have been carried out for decades to understand the functions of bio-molecules. Fluorescence, one of the popular spectroscopic techniques has been used rigorously to follow various bio-events. However, fluorescence suffers from certain limitations due to the insufficient availability of fluorescent bio-molecules. Covalent attachment of fluorophores with different bio-molecules provides a way of overcoming this problem. Lipid, steroid, sugar, nucleic, and amino acid are the 5 main classes of bio-molecules although there are many other sub-classes. This review demonstrates the applications of such conjugated fluorescent molecular probes in different domains of biological activities. This also brings out the advantages and disadvantages of this particular type of fluorophores with the insight to the future perspectives. © 2018, © 2018 Taylor & Francis Group, LLC.