Indium-filled carbon nanotubes were synthesized via a simple chemical vapor deposition. The carbon nanotubes had diameters of 100-200 nm and length of; 10mm. The melting and expansion behavior of the indium in carbon nanotubes were investigated in an analytical transmission electron microscope. It was found that the melting and expansion behavior of indium were different from that in a macroscopic state. The melting behavior was explained using a particular equation developed for a nanoscale indium column. The analysis of the expansion behavior allows us to clarify the problems of indium filling usage in carbon nanotube-based nanothermometer.