howclose.to
THE TREE

An honest tech tree for civilization

How close are we?

Tracked by milestone, metric and setback.

20 bottleneck technologies. What is proven, what remains, and what it could unlock.

AS OF JULY 2026

The example · Nuclear Fusion

Can we bottle a star?How close are we to fusion power?

The record

19201920✓Eddington proposes stellar fusion1934✓Fusion achieved in a lab1958✓The tokamak is born1968✓T-3 stuns the field1983✓JET switches on1991✓First controlled fusion power1997✓JET record: Q = 0.672006✓ITER agreement signed2021✓Private fusion waveDEC 2022✓NIF achieves ignitionFEB 2024 · HERE✓NIF ignites repeatedly, gain ~2.42027SPARC targets Q > 10~2035ARC - first electricityUNLOCKS →Low-carbonelectricity atscaleMore flexible cleanpowerPotential climatetools
20 technologies · five fields01 / 04 · Explore the problems ↓

Section 02 · The problems, by fieldSection 02 · The problems, by field

Everything we're trackingThe full register, grouped by domain

20 hard problems. 5 fields. Each with a different next step.Each field has its own bottlenecks and next tests. Ordering within a field is editorial, not a ranking.

5 fields · 20 problems
Energy4 tracked
Clean HydrogenClean hydrogen could fuel steel, ships, and fertilizer. First it has to get cheap - and get built at scale.Electrolysis works; the open question is whether clean hydrogen can reach a few dollars a kilogram and scale to industrial volumes.Electrochemical AmmoniaSmall cells can now make ammonia from nitrogen reliably for days, but they are still far too slow and energy-hungry to replace an ammonia plant.Verified lithium-mediated cells now combine high selectivity with continuous operation, but no system has simultaneously demonstrated industrial current density, energy efficiency, scale and lifetime.Enhanced geothermalHot rock is everywhere underground. The race is to build the plumbing to reach it - cheaply, safely, and at the scale of a real power plant.The physics of engineered reservoirs is proven; the open question is whether they can be drilled cheaply, run for years, and financed at utility scale.Nuclear FusionWe have made a tiny star flash in a laboratory; now we have to turn that flash into a dependable power station.Fusion has crossed scientific breakeven, but an economical power plant still requires a much harder engineering breakeven.
Biology & Health4 tracked
100-Day VaccinesCOVID took 326 days. The target for the next pandemic is 100 - a vaccine before the outbreak spirals.COVID compressed vaccine development from years to months; the goal is a repeatable 100 days from a new pathogen to authorized shots.Healthy LongevityWe can slow parts of aging in animals; proving that people gain many healthy years will take long, careful trials that are only just starting.Multiple interventions now reproducibly slow aging in mice, but no treatment has yet shown a large, durable extension of healthy lifespan in humans.Speech BCIElectrodes read the brain's signals for speech. The race is to make them fast, accurate, and durable enough for daily life.Implanted electrodes can already turn neural activity into words on a screen; the open questions are speed, vocabulary, and whether it lasts for years.XenotransplantThousands die waiting for organs. Gene-edited pig kidneys and hearts could close the gap - if they last.Gene-edited pig organs have kept people alive for months; the open question is whether they can replace human donors for years, not weeks.
Intelligence & Machines5 tracked
AGIAI can already help with many kinds of thinking, but it still makes confident mistakes and struggles to carry a big job through on its own.Frontier models saturate most static benchmarks, yet reliable long-horizon autonomy, calibrated reasoning and a shared definition of general intelligence all remain open - so any single 'percent to AGI' is a guess dressed as a number.Brain ConnectomicsResearchers have mapped a whole fly brain and a tiny piece of mouse brain. The hard part is scaling that detail across an entire mammal without losing or inventing connections.A whole adult fly is mapped at synapse resolution and a mouse cortical fragment now contains more than half a billion detected synapses; the whole mouse remains an estimated three orders of magnitude larger.DNA Data StorageDNA can hold computer files in an extraordinarily small sample. The missing step is a useful machine that writes a large archive quickly, finds one file and costs less than today's cold storage.Synthetic DNA has recovered a 200 MB random-access archive without bit errors and automated a complete write-to-read cycle for five bytes, but no public benchmark joins useful payload, throughput, retrieval and cost.Fault-Tolerant QuantumToday's quantum computers are too error-prone to trust. Fixing that means going from a handful of good qubits to millions.Error-corrected qubits have crossed below threshold; the open question is scaling from one logical qubit to the millions a useful machine needs.General RoboticsRobots can walk, run and keep their balance beautifully now. The hard part left is hands and judgment: doing varied tasks all day, safely, without a human quietly steering.Legged locomotion is essentially solved, but dexterous manipulation and open-world autonomy are not, so today's factory and home robots run narrow, supervised, and heavily teleoperated.
Materials2 tracked
Near-Zero CementMaking cement pumps out huge amounts of CO2. New recipes and capture can slash it - if they stay cheap enough to use everywhere.Cement is about 8% of global CO2; low-clinker chemistries and carbon capture can cut it deeply, but not yet at commodity cost and scale.Room-temp SuperconductorsMaterials squeezed to crushing pressures lose resistance when nearly warm, but nothing verified works in an ordinary room - and the loudest recent claims turned out to be wrong.Superconductivity near room temperature has only been credibly observed under megabar pressures; every ambient-pressure room-temperature claim has failed replication or been retracted.
Earth & Space5 tracked
Cheap Space LaunchRockets can now land and fly again, which made space far cheaper - but the truly cheap ticket needs a whole rocket you can reuse in days, and nobody has that yet.Reusable first stages have cut the price of orbit by more than 90% since the Shuttle, but the sub-$100/kg goal depends on rapid full reuse that Starship has not yet demonstrated.Closed-Loop Life SupportThe space station recycles almost all its water, but a self-sustaining habitat still has to close air, food and waste loops at the same time.Water recycling is near exploration grade in orbit, but oxygen, food, waste and maintenance have never been closed together beyond Earth.Direct Air CaptureMachines can already pull carbon from the sky. The challenge is doing it cheaply - and a million times bigger.Plants that pull CO2 straight from the air are running; the open question is cost per tonne and scaling from thousands to billions of tonnes.Exoplanet BiosignaturesWe know more than 6,000 planets beyond our Solar System, but zero confirmed living ones. The next leap needs a telescope that can separate an Earth-like planet from a star ten billion times brighter.Atmospheric spectroscopy is now routine for some large exoplanets, but no world beyond Earth has yielded a confirmed biosignature; the observatory intended to survey nearby potentially habitable worlds remains in development.Planetary DefenseWe have moved one harmless asteroid. The bigger gap is seeing a dangerous one early enough: more than half of the estimated regional-size population is still unknown.Humanity has demonstrated one asteroid-deflection technique, but the survey needed to find regional-scale threats is only halfway to its statutory goal.
02 / 04 · 20 technologies · 5 fieldsBrowse the full A–Z register →↓ next — The whole tree

Section 03 · The whole tree · figure 1 of 2figure 1 of 2

Twenty problems. Different distances to go.Twenty problems. Different distances to go.

Stages show what has been demonstrated. Links show recorded dependencies.A technology moves through stages. Tap a problem to see what it needs and what it opens.

5 fields · 20 problems
The whole tree, arranged by maturity stageTracked technologies move from lab demonstration through engineering and scaling. The deployed column is intentionally empty.LAB DEMOLABProof of concept in controlled settings.ENGINEERINGENGWorking systems at meaningful scale.SCALINGSCALECost-competitive, robust and replicable.DEPLOYEDDEPLOYWide, durable, global benefit.STAGES ARE NOT PERCENTAGESElectrochemical AmmoniaFault-Tolerant QuantumGeneral RoboticsHealthy LongevityRoom-temp SuperconductorsSTALLED100-Day VaccinesAGIClosed-Loop Life SupportDNA Data StorageEnhanced geothermalExoplanet BiosignaturesNuclear FusionPlanetary DefenseSpeech BCIXenotransplantBrain ConnectomicsCheap Space LaunchClean HydrogenDirect Air CaptureNear-Zero CementNO DEPLOYED RECORDS YET
Read the map as a list

Lab demo

Engineering

Scaling

Stages left to right: lab demo · engineering · scaling · deployedStages are not completion percentages.hollow node = recorded stagedashed link = dependencydashed mark = stalled

Map node key · stage

  1. 01Electrochemical AmmoniaLab demo
  2. 02Fault-Tolerant QuantumLab demo
  3. 03General RoboticsLab demo
  4. 04Healthy LongevityLab demo
  5. 05Room-temp SuperconductorsLab demo
  6. 06100-Day VaccinesEngineering
  7. 07AGIEngineering
  8. 08Closed-Loop Life SupportEngineering
  9. 09DNA Data StorageEngineering
  10. 10Enhanced geothermalEngineering
  11. 11Exoplanet BiosignaturesEngineering
  12. 12Nuclear FusionEngineering
  13. 13Planetary DefenseEngineering
  14. 14Speech BCIEngineering
  15. 15XenotransplantEngineering
  16. 16Brain ConnectomicsScaling
  17. 17Cheap Space LaunchScaling
  18. 18Clean HydrogenScaling
  19. 19Direct Air CaptureScaling
  20. 20Near-Zero CementScaling
03 / 04 · stages are not percentages↓ next — Figure 2 · The Interchange

Section 04 · The interchange · figure 2 of 2figure 2 of 2

Five fields. An unfinished destination.Five fields. An unfinished destination.

Each field is a route through maturity stages. The final stretch toward Deployed is unbuilt track.Read it like a transit map. Every line has a different last station; the destination is still being built.

solid route · dashed route still to build
The Interchange: five fields converging on an unfinished destinationFive domain lines pass through maturity zones. Solid routes end at each field's latest recorded station; dashed track marks the unbuilt route toward deployment.THEORETICALTHRYLAB DEMOLABENGINEERINGENGSCALINGSCALEDEPLOYEDDEPLOYNO ARRIVALS YETENERGYMATERIALSINTELLIGENCE & MACHINESBIOLOGY & HEALTHEARTH & SPACETHE LAST STATIONIS UNBUILT.ElectrochemicalAmmoniaEnhancedgeothermalNuclear FusionClean HydrogenRoom-tempSuperconductorsSTALLED · NO SERVICENear-ZeroCementFT QuantumGeneralRoboticsAGIDNA DataStorageBrainConnectomicsHealthyLongevity100-DayVaccinesSpeech BCIXenotransplantClosed-LoopLife SupportExoplanetBiosignaturesPlanetaryDefenseCheap SpaceLaunchDirect AirCapture
Stage order: theoretical · lab demo · engineering · scaling · deployedLines: energy · materials · intelligence · biology & health · earth & spaceline = fieldzone = maturity stagesolid route = recorded stationsdashed track = route still to builddashed station = stalled

Station key · field and stage

  1. 01Electrochemical AmmoniaEnergy · Lab demo
  2. 02Enhanced geothermalEnergy · Engineering
  3. 03Nuclear FusionEnergy · Engineering
  4. 04Clean HydrogenEnergy · Scaling
  5. 05Room-temp SuperconductorsMaterials · Lab demo
  6. 06Near-Zero CementMaterials · Scaling
  7. 07Fault-Tolerant QuantumIntelligence & Machines · Lab demo
  8. 08General RoboticsIntelligence & Machines · Lab demo
  9. 09AGIIntelligence & Machines · Engineering
  10. 10DNA Data StorageIntelligence & Machines · Engineering
  11. 11Brain ConnectomicsIntelligence & Machines · Scaling
  12. 12Healthy LongevityBiology & Health · Lab demo
  13. 13100-Day VaccinesBiology & Health · Engineering
  14. 14Speech BCIBiology & Health · Engineering
  15. 15XenotransplantBiology & Health · Engineering
  16. 16Closed-Loop Life SupportEarth & Space · Engineering
  17. 17Exoplanet BiosignaturesEarth & Space · Engineering
  18. 18Planetary DefenseEarth & Space · Engineering
  19. 19Cheap Space LaunchEarth & Space · Scaling
  20. 20Direct Air CaptureEarth & Space · Scaling
Read each field route as a list

Energy

  1. Electrochemical AmmoniaLab demo
  2. Enhanced geothermalEngineering
  3. Nuclear FusionEngineering
  4. Clean HydrogenScaling

Materials

  1. Room-temp SuperconductorsLab demo · stalled
  2. Near-Zero CementScaling

Intelligence & Machines

  1. Fault-Tolerant QuantumLab demo
  2. General RoboticsLab demo
  3. AGIEngineering
  4. DNA Data StorageEngineering
  5. Brain ConnectomicsScaling

Biology & Health

  1. Healthy LongevityLab demo
  2. 100-Day VaccinesEngineering
  3. Speech BCIEngineering
  4. XenotransplantEngineering

Earth & Space

  1. Closed-Loop Life SupportEngineering
  2. Exoplanet BiosignaturesEngineering
  3. Planetary DefenseEngineering
  4. Cheap Space LaunchScaling
  5. Direct Air CaptureScaling
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