Greubel Forsey has unveiled the Nano Foudroyante, a watch that features a flyback chronograph with a flying tourbillon and a Nano Fourdoyante. A limited edition of 22 pieces, it is the first official version of this watch – first introduced last year as the Nano Foudroyante EWT (Experimental Watch Technology). The EWT marked the brand’s 20th anniversary and was their “10th Fundamental Invention.”
Image: The Nano Foudroyante EWT of last year – both dial and caseback side. A limited edition of 11 pieces. Notice the olive-domed jewels in gold chatons on the bridges, the engravings on the caseback, and the “gold security screws” that secure the caseback to the main case. Its case is made from white gold and tantalum – the latter incredibly difficult to machine.
After a hiatus of two years, Greubel Forsey has entered the Nano Foudroyante in the Mechanical Exception category of the Grand Prix d’Horlogerie de Genève (GPHG) awards, scheduled to be held in Geneva, Switzerland on 13th November 2025.
Key Features
Functions
Image: Notice the Nano Foudroyante’s dial on the flying tourbillon. According to the Fondation Haute Horlogerie (FHH), a Foudroyante is defined as: “On a chronograph, a hand that makes one rotation every second, pausing four, five, even eight times to indicate quarters, fifths or eighths of a second.”
Hours and minutes. Small seconds displayed on subdial between 7 and 8 o’clock.
Off-centred 60-second flying tourbillon with Nano Foudroyante.
Chronograph functions: Central chronograph seconds hand with a flyback function. 60-minute counter displayed on subdial at 9 o’clock.
Dial
Image: The Nano Foudroyante’s dial – which rotates clockwise with the 60-second flying tourbillon – remains oriented at 12 o’clock. The red elements – Nano Foudroyante’s hand, arrow-shaped tourbillon pointer, markers at 12 o’clock on both the tourbillon seconds scale and outer 60-second flange – contrast well with the rhodium-coloured dial with blue elements. The tourbillon cage bridges are made from titanium, and feature “polished bevelling, straight-grained flanks, with engraved GF logo.” The counterweight is made from platinum.
Multi-level rhodium-coloured dial made from gold.
Hour and minute hands are made from polished blued steel and coated with Super-LumiNova. They feature a hand-polished countersink and a flat black polished head.
The Foudroyante dial is white with transferred numerals. It features a polished bevel with a flat black polished central plate.
The small seconds and 60-minute counter subdials feature a polished bevel. Their hands are made from polished blued steel and feature a hand-polished countersink and a flat black polished head.
All indications are engraved and lacquered. Outer minute-scale features a blue finish.
Movement
Image: Movement finishing of the bridges and main plate: “Nickel silver, frosted and spotted with polished bevelling and countersinks, straight-grained flanks, nickel-palladium treatment. Straight-grained and flat black polished steel chronograph mechanism, polished bevelling, straight-grained flanks. Three-dimensional column wheel, frosted and circular-grained, polished columns. Central seconds wheel, circular-grained, polished bevelling with relief-engraved texts. Gold plate, circular-grained, with engraved limitation number.”
Powered by a hand-wound flyback chronograph calibre with 2 patents. It drives the: hours, minutes, and small seconds; 60-second flying tourbillon with 1/6th of a second Fourdoyante; and central flyback chronograph seconds and 60-minute counter (semi-instantaneous).
Diameter: 31.60 mm. Thickness: 9.40 mm. Parts: 428. This includes the 142 parts of the tourbillon cage. Tourbillon cage weight: 0.835 g. Jewels 53. (The EWT – which has the same movement – has 42 jewels.) Frequency: 21,600 vph or 3 Hz. Chronometric power reserve: 24 hours with chronograph engaged. (Perhaps longer if chronograph not engaged.)
The movement features a “fast rotating barrel with a fixed main spring bridle.” The barrel completes 1 turn every 3.7 hours. Variable inertia or free-sprung balance wheel with “gold mean-time screws.” Diameter: 10 mm. Phillips terminal curve balance spring with a Geneva-style stud.
Nano mechanics explained
“At the heart of this timepiece lies a disruptive idea: nano mechanics – the control of energy at the nanojoule scale inside a mechanical movement. This paradigm shift enables the Nano Foudroyante to operate its eponymous complication using just 16 nanojoules per jump, compared to 30 microjoules in traditional designs – a staggering reduction by a factor of 1,800.
The complication divides each second into six segments using a lightweight, red-treated hand that rotates once per second, driven directly by the oscillations of the 3 Hz balance wheel. There is no traditional gear train; instead, a minimalist series of low-inertia wheels efficiently distributes energy through the movement.”
Case
Case is made from white gold. Caseband diameter: 37.90 mm. Bezel diameter: 38.30 mm. Thickness: 10.49 mm. Thickness with synthetic sapphire crystals: 14.34 mm.
Bezel is hand polished. Caseband features a “hand-finished straight-graining” finish. Dial side and caseback feature a “high domed synthetic sapphire crystal.” Crown with pusher at 3 o’clock is made from white gold engraved with the brand’s logo. Pusher at 2 o’clock is made from hand-polished white gold. Water resistant up to 3 ATM / 30 metres / 100 feet. The watch comes with a hand-sewn textured rubber strap fitted to a white gold pin buckle hand-engraved with the brand’s logo.
Our Thoughts
Image: Not classically beautiful, but that’s not the point of a Greubel Forsey. Their beauty lies in understanding them. The Nano Fourdoyante is no different. It marks an exciting new chapter for the independent watch brand which announced an updated shareholding structure earlier this year.
Last month when I wrote about the Balancier Contemporain in Stainless Steel Final Edition, I mentioned that watches with smaller diameters are a new direction for the brand. The Nano Foudroyante is housed in a smaller diameter case – but is in no way a “lesser watch” than prior creations from the brand.
Greubel Forsey is renown for complex horological innovations – not recreating what has been done 100-200 years ago, and exemplary movement finishing. The Nano Foudroyante – with its flyback chronograph, flying tourbillon with Nano Foudroyante, and movement finishing – lives up to everything the brand stands for. It is a horological masterpiece and a future icon. We wish them all the best for the GPHG awards.
Additional Details
Name: Nano Foudroyante
Price: Swiss Franc (CHF) 465,000 (excluding taxes)
Limited edition of 22 pieces.
Please visit the brand’s website and Instagram page for more information.
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