Femtosecond laser synthesis of fluorescent products from essential amino acids in living cells and tissues can be exploited in fluorescent bioimaging. To gain insight into reaction mechanism and a role of thermal processes we  examine synthesis of fluorescent products from L-lysine by femtosecond laser irradiation, hydrothermal and microwave synthesis and perform comparative analysis of reaction products. Our results indicate that compared with purely thermal synthetic routes femtosecond laser synthesis favours formation of carbon dots-type fluorescent nanomaterials.