The ornamental design for a nanogrid, as shown and described.
FIG. 1 is a front, right, top perspective view of a nanogrid, showing the new design;
FIG. 2 is a front, bottom, right perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The portions in broken lines of even length shown in the drawings illustrate portions of the nanogrid that form no part of the claimed design. The broken lines of uneven length shown in the drawings illustrate the boundary of the claimed design and form no part thereof. Contrast in materials is shown by line shading in some areas and stipple shading in other areas.