A needle probe for sensing compositional information, comprising: a needle having a tip region; a resistive element attached to the needle at the tip region; and a measurement system configured to 1) drive an electrical current through the resistive element to apply heating to the resistive element, and 2) measure an electrical response of the resistive element to the heating, wherein: the tip region comprises a tip region side surface and a tip region end surface, the tip region side surface encircling a longitudinal axis of the needle, the tip region end surface being at an extreme distal end of the needle, the longitudinal axis passing through the tip region end surface, characterized in that: the needle probe further comprises a processing unit configured to determine compositional information about material in contact with the tip region by analysing a variation of voltage with time in the measured electrical response of the resistive element to the heating, the variation of voltage with time being dependent on heat transfer characteristics of the material in contact with the tip region; the resistive element is a thin film resistive element mounted on a substrate in such a way that at least 10% of the surface area of the resistive element is in contact with the substrate, the thin film resistive element having a first surface configured to face towards the material to be sensed and a second surface facing towards the substrate; and the resistive element is attached to the tip region end surface. a needle having a tip region; a resistive element attached to the needle at the tip region; and a measurement system configured to 1) drive an electrical current through the resistive element to apply heating to the resistive element, and 2) measure an electrical response of the resistive element to the heating, wherein: the tip region comprises a tip region side surface and a tip region end surface, the tip region side surface encircling a longitudinal axis of the needle, the tip region end surface being at an extreme distal end of the needle, the longitudinal axis passing through the tip region end surface, characterized in that: the needle probe further comprises a processing unit configured to determine compositional information about material in contact with the tip region by analysing a variation of voltage with time in the measured electrical response of the resistive element to the heating, the variation of voltage with time being dependent on heat transfer characteristics of the material in contact with the tip region; the resistive element is a thin film resistive element mounted on a substrate in such a way that at least 10% of the surface area of the resistive element is in contact with the substrate, the thin film resistive element having a first surface configured to face towards the material to be sensed and a second surface facing towards the substrate; and the resistive element is attached to the tip region end surface. the needle probe further comprises a processing unit configured to determine compositional information about material in contact with the tip region by analysing a variation of voltage with time in the measured electrical response of the resistive element to the heating, the variation of voltage with time being dependent on heat transfer characteristics of the material in contact with the tip region; the resistive element is a thin film resistive element mounted on a substrate in such a way that at least 10% of the surface area of the resistive element is in contact with the substrate, the thin film resistive element having a first surface configured to face towards the material to be sensed and a second surface facing towards the substrate; and the resistive element is attached to the tip region end surface.