Whether you are brushing up for a quiz or just want to satisfy personal curiosity, this lesson makes cell biology simple. Beginning with the cellular membrane and working in toward the nucleus, learn about the basic structure of the cell and its organelles (such as ribosomes and the cytosol they float in.) After watching this video, you’ll also be able to distinguish between a eukaryote and a prokaryote. NOTE: All Khan Academy content is available for free at www.khanacademy.org.

Learn about the game theory problem known as the Prisoner's Dilemma with these concrete, step-by-step illustrations. This lesson includes a definition of the Nash equilibrium, a color-coded explanation of a payoff matrix, and an argument for why it is in the players' best interests not to cooperate. The theory behind the Prisoner's Dilemma has implications for economics, politics, and day-to-day human interaction. NOTE: All Khan Academy content is available for free at www.khanacademy.org.

Stir-frying is one of the simplest and most versatile methods of cooking. The technique does require planning and preparation, but each successive stir-fry you create will increase your confidence and improve your timing when it comes to cooking ingredients. In this lesson, learn what the five main components of a stir-fry are, and how they can be used to create infinite flavor combinations. Heavy on vegetables, stir-fries are some of the healthiest, quickest, and most delicious meals to make.

The quality of a stir-fry depends on the amount of preparation. Learn why it is important that vegetables be cut into similarly sized pieces, and why some should be blanched before being added to the wok. Every vegetable, spice, and herb contributes in some way to the appearance and texture of the dish (even the way the cut of the protein matters), so learn how to maximize each component! Lastly, if you desire moist and succulent meat in your stir fry, master the process known as velveting.

Pesto is a versatile Italian sauce—traditionally used on pizzas or pasta, it makes an excellent spread on sandwiches, potatoes or even fish (Chef Pesto prefers his on salmon). While there are many other ways to incorporate this sauce into your food, pesto itself is easy and quick to make. Chef Pesto prepares a basic recipe that can be augmented to satisfy your flavor cravings. Simple enough for a child to make, but delicious enough for everyone, enjoy some fresh pesto with dinner tonight!

Company A and Company B hold a duopoly on their industry. While they each might be tempted to flood the market and capture a larger market share, these two companies benefit most when they coordinate with each other. In this business and economics lesson from Khan Academy, learn how and why duopolistic competition works, and what it has to do with the Pareto Optimality and the Nash equilibrium. NOTE: All Khan Academy content is available for free at www.khanacademy.org.

You may be a pro at home brewing your own beer after watching James’ brewing lesson, but do you know when your beer is ready to be bottled? In this lesson, James demonstrates how to tell if the yeast has finished producing carbon dioxide (hint: watch the airlock), and how to package your beer. Make a trip to your local home brewing store to pick up items like a bottle filler or a capper— they’ll make the process easier and faster. After two weeks, sit back and enjoy the fruits of your labors.

Learn to take beautiful abstract photos of smoke. This lesson explains how to light smoke and set the correct exposure settings for great pictures - all without the use of a tripod. Phillip also teaches you how to process photos of smoke using Adobe Photoshop to create beautiful frameable photographs.

The stunning black and white photography of Ansel Adams has made him a household name, but for photographers, Adams is significant for more than this. Adams, and fellow photographer Fred Archer, developed a method of determining the best exposure for film, in order to create the best print—it’s called the Zone System. In this lesson from The Art of Photography, Ted describes how the system uses tonal mapping, and how you can fix blow-outs or increase tonal range, for a perfectly exposed image.

Learn how to improve your digital photography using HDR techniques. In this mini-photography course, Ted Forbes will give you tips on how to create HDR effects using Photoshop and Bridge. Apply these techniques to capture the full range of brights and darks in a scene to avoid over- and under-exposure.

Earth is about 4.5 billion years old, and the art of photography has been around for only the last two centuries— that is, about 1/281,250,000th of our planet’s history. But did you know that the principles of photography date back millennia; that in 400 BC, a Chinese philosopher described a pinhole camera, more than two thousand years before it would be created? In this lesson from The Art of Photography, learn how photography was developed, and get excited about where it is going!

Exposure, aperture, shutter - oh my! Demystify your SLR film or digital camera with this beginner’s lesson about photography, exposure, and manual camera settings. Ted Forbes will teach you about F-stops, and how to adjust shutter speed and aperture to get just the right exposure level. Apply these techniques to take high-quality portraits, landscape images, and action shots.

Though the creation of art is not formulaic, it does require more than luck and raw talent. In this photography tutorial, Ted Forbes discusses the elements required to create art, focusing on composition and the guideline known as the Rule of Thirds. Forbes illustrates the “golden mean” with examples by famous photographer Arnold Newman.