The Greubel Forsey Nano Foudroyante is a hand-wound flyback chronograph with a one-minute flying tourbillon and a miniature foudroyante, or lightning seconds, on the tourbillon cage. The white gold case measures 37.9 mm at the caseband and 38.3 mm at the bezel. It is 10.49 mm thick without the crystal and 14.34 mm including the high-domed sapphire, and water resistant to 30 m. The dial is rhodium-treated gold with a blue-coated hour and minute ring and blued steel hands. The movement has 428 components, 142 of them in the tourbillon cage, and 42 jewels. It beats at 3 Hz and runs for 24 hours with the chronograph engaged. The chronograph uses a column wheel, a vertical clutch and a patented clutch brake.

The foudroyante makes one turn per second in six steps. Greubel Forsey says each jump uses about 16 nanojoules, around 1,800 times less energy than a conventional lightning seconds, so it runs constantly without affecting balance amplitude. It is independent of the chronograph. The design first appeared in 2024 as the EWT (Experimental Watch Technology) Nano Foudroyante, the brand’s first chronograph, in white gold and tantalum. The 2025 version, presented in August, is the first limited edition, made in white gold only and limited to 22 pieces. It comes on a blue textured rubber strap with a white gold buckle. The price is CHF 465,000 before tax.

The Nano Foudroyante won the Mechanical Exception Watch Prize at the GPHG 2025. WatchesBySJX found it dense and solidly made, praised the chronograph construction as novel, and described the finishing as typical of the brand’s high standard. Its reservations were that the 2025 model looks too close to the EWT, that the foudroyante is not linked to the chronograph, and that CHF 465,000 is a lot for a chronograph. The 22-piece limited edition was announced in 2025 and was offered through Greubel Forsey and its retailers; no sources read confirm whether it has sold out as of October 2026.