Abstract: The present invention relates to, in a first aspect a handheld modular spectrometer comprising at least a light source, a detector, a sampling means and a processing unit, wherein at least the processing unit is within a spectrometer body that further comprises a connection node, at least the sampling means is within a spectrometer head module that attaches to the spectrometer body, the spectrometer head module further comprises a node interfacing means that interfaces with the connection node upon attachment of the spectrometer head module to the spectrometer body, and the attached spectrometer head module is able to be detached from the spectrometer body, enabling attachment of an alternate spectrometer head module also having a sampling means and node interfacing means, so as to alter at least one functional property of the handheld modular spectrometer.