Instead of any arduous philosophical discussions that aim to discern how we acquire happiness — here’s an inside-out approach, with the neurotransmitters in the brain taking the spotlight.

There are four primary chemicals in the brain that contribute to our happiness: serotonin, dopamine, oxytocin, and endorphins.

It’s important to note that these neurotransmitters are extremely complex.

And while they all have many different functions, the following shows their roles as they pertain to happiness and positive feelings in our lives.

1.) Serotonin. Produced for the most part in our digestive tract, serotonin is often regarded as the happy hormone, notes Medical News Today and other sources.

This neurotransmitter has a significant relationship to emotions, memory, sleep patterns, appetite, digestion, and even temperature regulation in the body.

When stress decreases, serotonin increases. As one of the two main neurotransmitters targeted with anti-anxiety and anti-depressant medication, serotonin can be thought of as a powerful mood stabilizer.

Natural ways to boost and support serotonin levels include exercise, eating carbohydrates, and eating foods high in L-tryptophan, such as chicken, beef, turkey, eggs, salmon, and green peas. Although there are healthier, complex carbohydrate alternatives to many simple carbohydrates, the fact that eating them is associated with a calming serotonin boost may be one of the reasons that bread and pasta can be so hard to put down.

Related: Most Delicious Fall Foods Are Good for Us, Too

2.) Dopamine. Known as the reward chemical — though its complexity should not be underestimated —dopamine release is associated with pleasurable activities, gratifying situations and even the anticipation of such activities and situations.

It plays a huge part in addiction, and dopamine is even released when any of us receive or even anticipate receiving “likes” on social media.

We have dopamine to thank for the brief yet undeniably present ego boost and rush we get as we observe the likes and comments build up.

But it’s not all daunting: Dopamine is also released when we accomplish a goal, overcome an obstacle, or achieve something that, frankly, makes us feel good about ourselves. As the latter of the two major targets of anti-depressant and anti-anxiety medication, dopamine can have a huge impact over mood as low levels are associated with apathy, decreased motivation, insomnia, fatigue, moodiness, concentration difficulties, even sugar cravings.

Things that boost this multifaceted brain chemical include exercise, massage, listening to music, meditation, and eating foods rich in the amino acid essential to its production — tyrosine — such as avocados, chicken, eggs, beans, fish, bananas, and almonds.

3.) Oxytocin. Known mostly as the love hormone or the bonding chemical, oxytocin is released when we connect with a loved one, bringing about feelings of warmth and security.

Natural ways to boost oxytocin include embracing a loved one, helping others, listening to music (and singing), practicing yoga, being with pets, and more.

When friends hug, when a couple cuddles, or when a mother gives birth, oxytocin is released in various amounts. It’s even one of the reasons breastfeeding can be such a bonding experience for both mother and child, as the powerful and influential oxytocin not only stimulates the production of both serotonin and dopamine but also reduces levels of cortisol, the stress hormone.

Natural ways to boost oxytocin include embracing a loved one, helping others, listening to music (and singing), practicing yoga, being with pets, receiving acupuncture or massage treatments, socializing with others — and just about anything else that decreases stress.

Related: Yoga’s Five Spectacular Benefits: Say Yes to It!

Additionally, Vitamin D, Vitamin C, magnesium, taurine, caffeine, and an overall healthy diet support production of this brain chemical.

4.) Endorphins. Naturally functioning in the body, endorphins act as organic painkillers as they engage the brain’s opiate receptors, just as many prescription painkillers such as morphine and codeine do. In fact, humans wouldn’t even be able to get “high” off opiates if we weren’t born with such receptors.

Once they’re released into the brain, these hormones work to lower the perception of pain, while also prompting feelings of positivity and euphoria (without risk of drug addiction).

Though endorphins are primarily thought to combat stress and pain, they are also released with exercise (such as in a runner’s high), meditation, music, UV light, and even light-to-moderate alcohol consumption.

Foods and nutrients that encourage the release of endorphins include dark chocolate, hot peppers, vanilla extract, ginseng, and comfort food in general.

And here’s a good reminder, in conclusion: Exercise is the best way to give all happiness-related chemicals a boost.