This seminar in writing introduced novel cancer thermal therapy using functionalized heat-generating nanoparticles with about 100 nm diameter, administered via intratumor injection. The nanoparticles named magnetites cationic lipid composite particles (MCL particles) were composed of about 10 nm magnetites (Fe₃O₄), a cationic lipid and two neutral lipids. Magnetites in MCL particles generated heat due to external alternating magnetic field (AMF) irradiation to kill cancer cells nearby located. A cationic lipid component conferred several functions to MCL particles necessary for its efficacy and safety. Origination of the therapy with MCL particles was summarized by referring to our earlier reports in 1996-2014. Further characterizations of MCP particles and utility of heat dose index for treatment control were summarized by referring to our recent reports in 2019-2022. Unpublished data were supplemented to support overall understanding of the therapy. Purpose of this seminar is to clarify novel principle of the therapy in comparison with conventional thermal therapies and to discuss its clinical application.