Our 2026 Review of California State Summer School for Mathematics and Science for High Schoolers (COSMOS)
Updated: Sep 2
Updated September 1, 2026
TL;DR
COSMOS is a selective, four-week residential STEM program open to California high schoolers, run across six UC campuses. For the 2026 cycle, tuition ran $5,518 plus a $46 application fee, applications opened January 7 and closed February 6, and each cluster capped enrollment at 20 to 25 students. It's a legitimate, UC-backed way to go deep on a STEM topic and get a taste of college life, though it's not free and it's California-residents-only. If you want a research experience that isn't capped at four weeks or restricted to one state, the Lumiere Research Scholar Program pairs you 1-1 with a PhD mentor for an independent research paper.
Participating in research programs during high school can significantly enhance your profile and skill set as you apply to college. These programs allow you to engage deeply with a field of interest, often beyond the scope of your high school curriculum. You will develop a thorough understanding of the field and its career paths while being mentored by researchers in the field. You will also likely build a valuable network of peers, university faculty, and industry professionals.
In addition, by finding, applying for, and participating in one of these programs, you can demonstrate your intellectual curiosity to college admissions officers. Many universities carefully note these traits, and participating in a prestigious research program can help you stand out during college admissions.
In this blog, we will review one such program: the California State Summer School for Mathematics and Science (COSMOS).
What is COSMOS?
COSMOS is a four-week residential summer program for California high school students interested in mathematics, science, engineering, or technology.
COSMOS isn't a single-campus program. It runs across six University of California campuses: UC Davis, UC Irvine, UCLA, UC Merced, UC San Diego, and UC Santa Cruz. You apply to just one campus, and each campus runs its own curriculum and its own set of "clusters," specialized tracks focused on advanced STEM topics designed and taught by that campus's own faculty. That means the experience (and the specific clusters on offer) genuinely differs by campus. You can see the full campus-by-campus cluster list on the COSMOS Statewide site.
This guide focuses on the UC Santa Cruz site, since it's the most established and most searched-for COSMOS campus. Its current clusters are:
Number theory and discrete math
Nanochemistry and nanotechnology
Making an animal: development and bioinformatics
Quantum information science and engineering (QISE)
Video games: the design of fun from concept to code
Introduction to smart and sustainable power
Shining a light on the future: the photonics revolution in healthcare, energy, and information technologies
Practical applications of chemical principles
Molecular biology investigations
Semiconductor materials and device engineering
Fundamentals of machine learning in robotics
Exploring the structure of quantum materials by neutron scattering and x-ray diffraction
Crystalline quantum materials (QCM): intersections between physics, chemistry, and materials science
Most clusters have prerequisite coursework; check the full cluster descriptions before you apply, since faculty won't consider you for a cluster you don't meet the prerequisites for.
In addition to your cluster, you'll attend the Discovery Lecture Series, where researchers present on current work across a range of STEM fields. Attendance is mandatory and open to the wider campus community.
What do COSMOS students actually work on?
Every COSMOS student develops an independent research topic connected to their cluster, working with cluster faculty and course assistants (typically UCSC graduate students) and using university lab and library resources to carry it out over the four weeks. Past cluster topics have ranged from quantum materials characterization to machine learning applications in robotics to molecular biology investigations, so the actual day-to-day research looks different depending on which cluster you're in. Most clusters build toward a final presentation where students share their results with their cohort.
If you're looking for a research experience with more one-on-one mentorship and a final paper (rather than a cluster-based group structure), that's the model the Lumiere Research Scholar Program uses instead.
What does a typical day at COSMOS look like?
A typical day includes lectures, cluster time, recreational activities, and more. Here's a sample schedule:
[Source: Sample dailly schedule from the official daily schedule page.]
How much does COSMOS cost?
For the 2026 cycle, tuition was $5,518, plus a $46 application fee. Tuition covers course and lab materials, housing, meals, and field trips.
Financial aid, up to the full cost of tuition, is available for qualifying California residents and is handled centrally through the COSMOS Statewide office, not by individual campuses. Applying for financial aid does not affect your admissions decision. You can apply through the COSMOS Statewide financial aid page.
Admitted students pay tuition in installments tied to their admission date, with the first third due shortly after acceptance and the remainder due a few weeks later. Full payment schedules are on the official tuition page.
Who can apply to COSMOS?
For the 2026 cycle, COSMOS was open to California residents entering ninth through twelfth grade in fall 2026 (in other words, rising eighth through rising eleventh graders), per COSMOS's own application page. You can only attend COSMOS once, even if you weren't admitted to your first-choice cluster or want to try a different campus.
How do you apply to COSMOS?
A complete COSMOS application includes:
An online application, including one personal statement
At least one teacher recommendation (two are recommended; STEM teachers preferred)
Unofficial transcripts, generated after the application opens (8th or 9th graders also submit 7th/8th grade report cards)
A parent or guardian e-signature
The application fee
An optional financial aid application
You'll also write short essays for your first- and second-choice cluster picks. Applying to more than one cluster at your chosen campus can improve your odds of admission.
Cluster faculty review every application and essay in full, weighing your fit against prerequisites and against other applicants to that cluster. Contact your recommenders early. The link to their recommendation form goes out as soon as you save your application, before it's complete.
Key COSMOS dates and deadlines
These are the confirmed dates for the 2026 cycle. 2027 dates have not been released yet — COSMOS says cluster information for next summer will be finalized by the end of November 2026, with applications opening in early January 2027. Check the official dates and deadlines page for updates.
Date (2026 cycle) | Milestone |
January 7, 2026 | Applications open |
February 6, 2026 | Application deadline (11:59 p.m. PST) |
March 26, 2026 | Admission decisions posted |
April 8, 2026 | Deadline to accept or decline; deposit and official transcripts due |
April 10 – May 27, 2026 | Waitlist offers made on a rolling basis |
July 5, 2026 | Program opens |
August 1, 2026 | Program closes |
How competitive is COSMOS? What is the acceptance rate?
It’s fairly tough, with an acceptance rate of 21%. Each cluster caps enrollment at 20 to 25 students, and the average unweighted GPA among applicants runs around 3.8, with most admitted students at 3.5 or above, according to COSMOS's own FAQ. Math and science grades carry the most weight in review.
COSMOS is endorsed by the University of California system and gives you access to UC faculty, labs, and research resources you wouldn't otherwise get in high school. That institutional backing is a meaningful part of what makes it selective and well-regarded.
Tips to strengthen your COSMOS application
Pick a cluster you're actually curious about, not the one that sounds most impressive. Faculty read your essay for genuine motivation, and cluster-specific essays that read as generic are easy to spot.
Apply to a second-choice cluster at the same campus. COSMOS lets you rank a first and second choice, and doing so can improve your odds.
Check prerequisites before you write your essay. Faculty won't consider you for a cluster you don't meet the coursework prerequisites for, regardless of how strong your essay is.
Request your recommendation early. The link goes to your teacher as soon as you save your application, not when you submit it, so give them time.
Be specific in your personal statement. Anchor it in an actual project, class, or moment that shaped your interest in STEM rather than general statements about "loving science."
Pros and cons of attending COSMOS
Pros
High-quality mentorship and network. You'll work directly with university faculty and researchers, both in your cluster and through the Discovery Lecture Series. These are people you can turn to later for research ideas, recommendation letters, and more.
Specialized STEM exposure. The cluster system lets you go deep on a specific advanced topic well beyond your high school curriculum, with access to UC labs, classrooms, and research infrastructure.
Campus experience. Living on a UC campus for four weeks gives you a real preview of college life, from dorm living to dining halls to weekend activities, plus a peer group of similarly STEM-motivated students.
Cons
Cost. Tuition covers room, board, and instruction, but the $5,518 total is out of reach for some families without financial aid.
California residents only. If you live outside the state, you're not eligible.
You only get one campus choice. Since clusters and curricula differ meaningfully by campus, picking the wrong campus for your interests means you can't switch or apply elsewhere the same cycle.
Less one-on-one mentorship than some alternatives. Much of the teaching happens at the cluster (group) level rather than one-on-one, which some students find less individualized than other research options.
Is COSMOS legit? Is it worth it?
Yes. COSMOS is a solid, UC-backed program that gives students real access to university-level STEM research, faculty mentorship, and lab resources. For students who can afford it (or who qualify for aid) and who pick a cluster they're genuinely excited about, it's a worthwhile investment in both academic depth and college-application substance.
That said, COSMOS alone isn't a guaranteed admissions boost. What matters more to colleges is what you actually did with the experience: the research question you pursued, what you learned, and where it took your thinking next. Treat it as a chance to go deep on a topic you care about, not as a line item.
If you want a STEM research experience that isn't capped at four weeks, isn't limited to California residents, and pairs you one-on-one with a mentor for an independent paper, check out the Lumiere Research Scholar Program, a selective online research program founded by researchers at Harvard and Oxford. Last year, over 4,000 students applied for 500 spots. You can find the application here.
Also worth a look: the Lumiere Research Inclusion Foundation, a non-profit research program for talented, low-income students. Last year, 150 students attended on full need-based financial aid.
Other California and research program options worth comparing
FAQ
What is the COSMOS summer program? COSMOS (California State Summer School for Mathematics and Science) is a four-week residential STEM program for California high schoolers, run across six UC campuses. Students join a "cluster" focused on an advanced STEM topic and complete an independent research project during the program.
How much does COSMOS cost? For the 2026 cycle, tuition was $5,518 plus a $46 application fee. Financial aid covering up to the full tuition amount is available for qualifying California residents through the COSMOS Statewide office.
Is COSMOS worth it? For students who pick a cluster they're genuinely interested in, yes: you get real UC faculty mentorship, lab access, and a research project you can speak to in college applications. It's not a guaranteed admissions boost on its own, and the cost is a real factor for some families without aid. If you want a longer, more individualized alternative, the Lumiere Research Scholar Program is worth a look.
How hard is it to get into COSMOS? It's competitive. Each cluster enrolls only 20 to 25 students, and the average unweighted GPA among applicants is around 3.8. COSMOS hasn't published a current program-wide acceptance rate, so treat any specific percentage you see online with caution unless it's sourced to an official page.
How long is COSMOS? COSMOS is a four-week residential program. The 2026 cycle ran from July 5 to August 1.
When does COSMOS open applications for 2027? Applications typically open in early January and close in early February. As of this writing, COSMOS says its 2027 cluster information will be finalized by the end of November 2026, with applications opening in early January 2027. Check the official dates page closer to that window for exact dates.
Can I attend COSMOS more than once? No. COSMOS only allows students to attend once, though you can reapply in a future year if you applied before but weren't admitted or didn't attend.
How do I list COSMOS on my college applications? List it under your activities section as an academic/research program: name it as "COSMOS (California State Summer School for Mathematics and Science)," note the campus you attended, the four-week duration, and briefly describe your cluster's research focus rather than just naming the program.
Stephen Turban is the co-founder of Lumiere Education and a graduate of Harvard College, where he earned an A.B. in Statistics before beginning a PhD at Harvard Business School. A former McKinsey & Company consultant and former researcher, his research has been covered by the Harvard Business Review, The Economist, BBC News, Freakonomics Radio, and the Washington Post. In his articles for Forbes, he writes on what students and professionals can learn from high school research, high school passion projects, critical thinking, and mentorship. At Lumiere, he leads a selective research program where students work one-on-one with a research mentor to develop an independent research paper. Connect with him on LinkedIn.