A system for exploration of the interior of an object, comprising: an interventional tool having a tip portion for introduction into the object; navigation equipment configured to produce current positional information indicative of a current position of the tip inside the object whilst the tool resides in the object; a probe for introduction into the object, configured to receive non-ionizing radiation reflected off the interior of the object; a spectral analyzer configured to spectrally analyze the received radiation into exploratory information about material composition and/or tissue structure of the object's interior at or around the current tip position of the interventional tool, the exploratory information comprising at least one measurement value for a material type present at or around the current tip position of the interventional tool and/or a scattering measurement value for an amount of scattering as per the received radiation; a graphical user interface generator configured to produce a graphics display on a display unit including, when displayed: i) at least one exploratory information indicator (412;612;1120;1220) for the scatter measurement value or for the material type measurement value or for a value derived from either or both of said measurement values; and ii) a position indicator (409;TP) for the current positional information of the tip's position in the object's interior; and the system further comprising: the display unit for displaying the graphics display when the system is used; characterised in that the exploratory information indicator comprises a) a pointer element (41 la-c;611;1115a-b; 1216a-c) configured to indicate a current reading of at least one of the measurement value or of a current reading of the derived value and b) a dial element (413a-c;613; 1215a-b) configured to indicate a range of values, with the pointer element being displayed against the dial element. an interventional tool having a tip portion for introduction into the object; navigation equipment configured to produce current positional information indicative of a current position of the tip inside the object whilst the tool resides in the object; a probe for introduction into the object, configured to receive non-ionizing radiation reflected off the interior of the object; a spectral analyzer configured to spectrally analyze the received radiation into exploratory information about material composition and/or tissue structure of the object's interior at or around the current tip position of the interventional tool, the exploratory information comprising at least one measurement value for a material type present at or around the current tip position of the interventional tool and/or a scattering measurement value for an amount of scattering as per the received radiation; a graphical user interface generator configured to produce a graphics display on a display unit including, when displayed: i) at least one exploratory information indicator (412;612;1120;1220) for the scatter measurement value or for the material type measurement value or for a value derived from either or both of said measurement values; and ii) a position indicator (409;TP) for the current positional information of the tip's position in the object's interior; i) at least one exploratory information indicator (412;612;1120;1220) for the scatter measurement value or for the material type measurement value or for a value derived from either or both of said measurement values; and ii) a position indicator (409;TP) for the current positional information of the tip's position in the object's interior; and the system further comprising: the display unit for displaying the graphics display when the system is used; characterised in that the exploratory information indicator comprises a) a pointer element (41 la-c;611;1115a-b; 1216a-c) configured to indicate a current reading of at least one of the measurement value or of a current reading of the derived value and b) a dial element (413a-c;613; 1215a-b) configured to indicate a range of values, with the pointer element being displayed against the dial element. the display unit for displaying the graphics display when the system is used; characterised in that the exploratory information indicator comprises a) a pointer element (41 la-c;611;1115a-b; 1216a-c) configured to indicate a current reading of at least one of the measurement value or of a current reading of the derived value and b) a dial element (413a-c;613; 1215a-b) configured to indicate a range of values, with the pointer element being displayed against the dial element.