Y Combinator’s latest Demo Day showcased a cohort of startups that leaned heavily into deep tech innovations, impressing venture capitalists with ideas that seemed almost like science fiction. Unlike previous batches, these startups presented grounded valuations, reflecting pragmatic expectations amid ambitious technological advances. TechCrunch polled early-stage VCs to highlight the nine most talked-about startups, each offering unique solutions to complex problems in various cutting-edge fields.

One standout is Atomarine, which aims to address the power shortage for data centers by creating floating centers powered initially by gas and eventually by nuclear reactors on barges at sea. This approach leverages the ocean for cooling and has already attracted over $4 billion in letters of intent, making it one of the highest-valued companies in this batch. Dipole Labs is focused on improving AI data center efficiency with a novel optical switch that eliminates energy-heavy conversions between light and electricity, reducing waste in GPU communication.

Isengard Industries, another highlight, develops jet-powered attack and counter-drones that can be locally manufactured in allied countries, offering a more cost-effective alternative to traditional prime contractors. Co-founded by former military personnel, the startup has generated $10 million in revenue and is gaining strong investor interest. Meanwhile, other companies like Lamb Labs work on ultra-efficient AI inference chips with hardcoded model weights to overcome energy bottlenecks, and Praxis Robotics collects real-world human work data to train robots capable of handling industrial tasks.

Additional remarkable startups include Nori, which is delivering affordable humanoid robots for household chores at a fraction of typical prices, and Cosmic Robotics, building autonomous heavy-lifting robots with sights set on Mars colonization, backed by $25 million in contracts through 2027. Parasma explores training human brain cells to power computing, while Waddle Labs uses AI-generated code to control robots via natural language, promising a new level of robotics programmability. These ventures represent a bold mix of futuristic technology with tangible commercial potential, signaling exciting directions for the next wave of innovation.