A microfluidic sample chip to test biological samples, especially for a PCR-type and/or fluorescence assay. The chip being in the shape of a hollow block having at least one chamber delimited by an upper wall, a lower wall and at least one side wall, into which a sample can be introduced for testing. The lower wall of the block is made of a material with a high thermal conductivity and the upper wall is made of a material with a low thermal conductivity. Preferably, the upper wall is preferably permeable to radiation in the visible spectrum between 400 and 700 nm. The block having at least two openings through which the sample can be introduced into at least one of the chambers and through which the air present in the chamber can be evacuated when the sample is introduced.