Reaction vessel holder and molecule detection device

A reaction vessel holder for receiving a reaction vessel, the reaction vessel for containing a sample and having at least one portion that is substantially optically transparent to light of at least a first range of wavelengths, the reaction vessel holder comprising:

• a body having a high thermal conductivity, the body being arranged to thermally couple to and support the reaction vessel, the body being further arranged to thermally couple to a thermal device that heats or cools the reaction vessel holder and thereby the reaction vessel, the body comprising at least one transparent portion that is substantially optically transparent to the light of at least the first range of wavelengths, such that the optically transparent portion of the reaction vessel is adapted to face the transparent portion of the body such that light of the first range of wavelengths to and/or from the sample in the reaction vessel pass through the transparent portion.