7 Tips to get Admitted to COSMOS (California State Summer School for Mathematics & Science)

Updated October 2026

TL;DR

COSMOS is a four-week residential STEM program at six University of California campuses, open only to California high schoolers. The 2027 application opens January 6, 2027, and closes February 5, 2027. You apply to one campus and pick one cluster, a small group that studies one technical topic, and you need one recommendation from a STEM teacher. A typical COSMOS attendee has a GPA of 3.5 or higher, and the program costs $5,793, with financial aid available. This guide gives you the dates, the rules, and 10 tips for an application that shows you are ready. If you want to build your own research project with a professor or PhD mentor, you can explore the Horizon Academic Research Program.

Many summer programs offer hands-on STEM learning, but the depth and structure of the experience can vary considerably. The California State Summer School for Mathematics and Science (COSMOS) places you in a cluster focused on an advanced STEM topic, such as machine learning, quantum information, robotics, or biomedical modeling. UC faculty and researchers teach the courses, and the curriculum combines technical coursework with hands-on activities and a related project.

That structure should shape how you approach the application. Show that you are prepared for challenging scientific or quantitative work and can explain why a particular cluster matches your interests. If you’re comparing opportunities in the state, see our guide to summer programs for high school students in California.

What is COSMOS?

The California State Summer School for Mathematics and Science is an intensive four-week residential pre-college program for high schoolers who have shown strong ability in science, technology, engineering, and math. You live on a University of California campus and work with faculty, researchers, and scientists in labs and other university facilities.

You spend the four weeks in one cluster instead of sampling unrelated courses. A cluster includes two science or math courses plus a science communication course, along with labs, field activities, lectures, discussions, and a related research project. Because each cluster focuses on one subject, you get much deeper into a topic than you would in a general summer course.

What are the COSMOS dates and deadlines for 2027?

COSMOS lists these dates on its Dates and Deadlines page. The program dates themselves are not posted yet.

COSMOS keeps a waitlist, and the last group from the waitlist hears back on May 26, 2027. If you do not respond to an offer by the deadline, COSMOS treats it as declined.

Which campuses and clusters can you choose?

You can apply to one of six University of California campuses, and you cannot apply to more than one. Each campus runs its own clusters, and the list changes by year. The official Campuses and Clusters page lists the current options.

Recent clusters have covered topics such as:

• Quantum mechanics and nanotechnology
• Astrophysics
• Machine learning
• Data science and big data
• Mathematical modeling
• Robotics
• Biomedical sciences and computational biology
• Materials science
• Semiconductor engineering and quantum information science
• Video game design
• Photonics
• Marine science
• Engineering design and tissue engineering
• Computer science

Most clusters require certain high school courses, so read the prerequisites before you choose. If you have a question about them, contact the campus directly.

Who can apply to COSMOS?

COSMOS is open to California high schoolers only. For 2027, you must be a rising 9th grader (starting 9th grade in fall 2027) through a rising 12th grader. International applicants and out-of-state applicants are not eligible. If your residency is unclear, contact the Statewide Office.

A few more rules apply:

• You apply to one campus, with a first choice and a second choice cluster.
• You can attend COSMOS only once, so people who have gone before cannot apply again.
• You must live on campus if you are admitted.
• COSMOS says that a typical attendee has a GPA of 3.5 or above.

That GPA is a pattern, and your coursework, your projects, and how well you fit your cluster matter too.

What do you submit?

Your application includes:

• An online application with one personal statement and a cluster choice essay
• One teacher recommendation, which must come from a STEM teacher, with a second one strongly recommended
• An unofficial transcript uploaded as a PDF, created after the application opens
• Report cards from earlier grades if you are applying as a younger high schooler
• A parent or guardian signature and the application fee, which a parent or guardian pays through a separate portal

If you are admitted, you also send an official transcript. COSMOS does not use SAT or ACT scores.

Is COSMOS competitive?

Yes, COSMOS is competitive. Each campus has limited space, and COSMOS says that it bases admission on the academic merits of your application in relation to the topic you chose. It does not publish an acceptance rate, so ignore any website that quotes an exact percentage without an official source. Each campus takes roughly 160 to 200 people, according to the program overview.

Because the review looks at fit, a strong application can still miss if it points at a cluster you are not ready for. Meeting the eligibility rules does not guarantee a spot.

How much does COSMOS cost, and can you get financial aid?

The 2027 program cost is $5,793, according to the dates and deadlines page. The application fee is $46, and a heading on the same page shows $48, so confirm the amount in the application portal. The program fee covers housing, meals, orientation, field trips, activities, and on-site support.

You pay in two steps. One-third is due on April 7, 2027, and the rest is due on April 16, 2027; both payments are non-refundable. A card payment adds about a 2.5% service fee, and you can avoid it by paying with a check or money order.

Financial assistance is available, and you apply for it separately. COSMOS reviews aid based on factors such as family income, family size, and available resources, and it does this separately from admission, so asking for aid does not hurt your chances. You hear about aid when you hear about admission. COSMOS does not list a stipend, and the program does not grant college credit.

What do you study, and what skills do you build?

The exact tools depend on your cluster. Depending on yours, you may work on:

• Quantitative problem solving
• Experimental design, data collection, and interpretation
• Mathematical modeling
• Programming and computation
• Laboratory techniques
• Engineering design and iteration
• Reading and discussing scientific ideas
• Science communication and technical presentations
• A related research project

That is why reading the cluster descriptions before you apply is one of the best things you can do. The cluster you pick shapes what you do for four weeks.

How to Get Into COSMOS: 10 Application Tips for 2027

1. Choose a cluster you can explain

You are applying to a specific academic environment, not a general camp. Read the cluster descriptions, the prerequisites, and the work involved before you choose your campus. If you pick a machine learning cluster, be ready to say why computational methods interest you. If you pick a biomedical cluster, show a link to biology, chemistry, math, or computation. COSMOS also asks for a second choice cluster, so pick one that fits you almost as well as your first.

2. Show your preparation with evidence

Look at the pattern in your transcript. For an engineering cluster, math and physics matter. For computational biology, biology, chemistry, math, or computer science can help. For data science, statistics, calculus, and programming are relevant. You do not need every advanced course your school offers. You need to show that you challenged yourself with what was available to you.

3. Build depth, not a long list

Fifteen unrelated STEM activities say less than a few connected ones. Suppose you like robotics. A list of a club, a science fair, a coding course, and a camp tells a reader little. A thread tells more: you learned basic programming, used it in a robot, hit a control problem, studied feedback systems, and changed your design. That shows growing technical depth.

4. Write your personal statement like a technical argument

Your statement is not an autobiography, and the space is limited. Answer a few questions: what interests you, how that interest grew, what you did with it, and what you want to investigate next. A specific story beats a big claim. Say a model you built failed under certain lighting, you tested different datasets, and you learned about image preprocessing. That gives the reader something real.

5. Pick recommenders who can describe how you think

COSMOS asks for one recommendation from a STEM teacher and strongly recommends a second, which can come from a counselor or another academic recommender. Your teachers answer questions about your STEM abilities and rank you against peers, and a formal letter is not required. All recommendations are due by the application deadline.

Choose people who can describe how you handle hard problems, react when a method fails, ask technical questions, and work with others. You will need their names and work email addresses, and some school email systems block COSMOS emails, so ask your teachers to check their spam folders.

6. Connect your experience to research

You do not need a published paper. You need to show that you think like a researcher, which starts with a question instead of an answer. A science project, a coding project where you tested different approaches, a math investigation, a lab experiment, an engineering prototype, or a project where you changed your hypothesis after seeing results all count. COSMOS builds a research project into each cluster, so this is a direct fit.

7. Show range within one direction

Being focused is different from being narrow. You can have one main interest and still show how it connects to other subjects, which matters because COSMOS clusters cross subject lines. You do not need to claim you have mastered those fields. You need to show that you see the connections and want to learn more.

8. Treat the cluster choice essay as its own piece

The application asks you to write about your cluster choices, with a word limit set by the text box. Do not reuse your personal statement. Use this space to name what in that cluster’s description matches your experience, and what you hope to learn. A reader should finish it knowing why you picked that cluster over the others.

9. Work backward from the deadline

COSMOS does not take late materials, and an incomplete application is not reviewed. Your unofficial transcript must be created after January 6, 2027, so you cannot upload one from last fall. A parent or guardian pays the application fee and signs through a separate portal. Ask your teachers for recommendations in December, and plan to finish at least a week before February 5.

10. Plan for the cost early

Talk to your family about the $5,793 cost before you apply. If you need aid, the aid form must be postmarked by February 6, 2027, and COSMOS recommends tracked mail. Aid is reviewed apart from admission, so you can apply for it without worrying about your odds.

What do past attendees say?

COSMOS shares alumni reflections and program updates on its campus sites. One reflection from UC Irvine mentions connections with other people in the program and with faculty, along with learning to present and reason about technical ideas.

Material from UC Davis describes working with faculty and researchers in advanced labs, and program newsletters describe work such as modeling DNA and RNA transcription, mathematical logic, electromechanical design, and robotics projects. You can read more on each campus page.

What are the strengths and considerations?

Strengths

• Specific clusters: You apply around one STEM interest instead of a general summer curriculum.
• Hands-on work: The program includes labs, field activities, discussions, and a related research project.
• Active faculty: UC faculty and researchers teach the courses.
• Technical range: Clusters cover fields from machine learning and quantum science to biomedical engineering and robotics.
• Residential setting: You spend four weeks living and learning on campus.

Considerations

• California only: The program is closed to out-of-state and international applicants.
• Competition: Space is limited at every campus, so eligibility does not guarantee a spot.
• Cluster fit: Your preparation needs to match the cluster you pick.
• Cost: The program costs $5,793 before any aid.
• Time: You commit to four weeks on campus.
• One campus: You cannot apply to more than one in a cycle.

Who is COSMOS best for?

COSMOS fits you if you already have a specific STEM subject or question you want to study more deeply. You do not need to know what you will study in college. You do need to be able to say which technical problems interest you right now.

If you like working through hard math problems, debugging code, designing experiments, building systems, or asking why a scientific effect behaves the way it does, COSMOS may match how you learn. It is less useful if you want a general college prep experience or a program with few academic prerequisites.

The best application is not the one with the most activities. It is the one where your coursework, projects, recommendations, and personal statement all point to the same academic interest. Before you submit, ask yourself: can your application show that you are ready to spend four weeks thinking hard about one difficult STEM problem?

How do you compare COSMOS with other programs?

Look past the name of any program. Check these points:

• Whether you work with faculty or with graduate researchers
• Whether the curriculum includes real research
• Whether you finish with a paper, presentation, or prototype
• Whether the program is residential
• Whether it has prerequisites
• Whether financial aid is available
• Whether international applicants can apply
• How selective it is

Residency rules matter as much as the subject. If you cannot apply to COSMOS because you live outside California, our list of competitive STEM programs for high school students covers more options, and our guide on how to get into a top high school research program explains how to build a strong application anywhere. You can also see our list of free summer programs for high school students in California.

If you want a competitive, mentored research program in areas like political theory, data science, machine learning, biology, or chemistry, consider the Horizon Academic Research Program.

Questions to ask before you apply to COSMOS

Image source: UC Davis