Zain is late for school and as he rushes to get ready, his heart is left pounding. Xoey & Yuri finds out what happens when the heart starts pounding and the inner workings of the heart that requires it to beat non-stop! Zain lambat ke sekolah dan sedang dia bergegas, Jantung mula berdegup cepat. Xoey dan Yuri dengan segera mengkaji misteri degupan jantung yang beritma LUB-DUB-LUB-DUB!

Zain falls from cycling and hurts his knee. Blood can be seen oozing out. Xoey & Yuri wonders how much blood does a person have and finds out more about how blood is made in the bone marrow. Zain terjatuh dan lututnya terluka! Dengan bantuan Sumsum Tulang, Xoey and Yuri mengkaji misteri jumlah darah dalam tubuh Zain yang tak pernah kehabisan.

Text Neck Syndrome? What is that?! Xoey & Yuri are intrigued by this phenomenon and finds out more about it through a meeting with the spine! Xoey dan Yuri mula rasa cemas apabila mereka belajar tentang Sindrom Leher Teks. Kata Tulang Belakang Zain mesti jaga postur tubuh. Tapi, kenapa?

Zain has always had a big appetite for a small boy and it always puzzles Xoey & Yuri as to where exactly does the food goes. They head down to the small intestines and finds out how important it is the kind of food we eat to maintain gut health. Zain berbadan kecil tapi dia mempunyai selera makan yang besar. Xoey dan Yuri berjumpa dengan Usus Kecil kerana mereka ingin tahu tentang perjalanan makanan dalam tubuh Zain.

Xoey & Yuri are alerted by a loud pop that sends them over to eardrum! They discover that the eardrums have more responsibility than to allow a person the ability to hear!

While climbing up the staircase, Zain finds himself gasping for air! This causes concern for Xoey & Yuri and they travel to lungs to get to the bottom of it. Xoey dan Yuri risau akan kesihatan Zain kerana dia termengah-mengah ketika menaiki tangga. Mungkin Paru-Paru tahu cara untuk membantu menjaga kesihatan Zain!

Zain is watching his father carrying weights, and decides to do the same but can't. Xoey & Yuri are wondering if bigger muscles actually mean more strength and discovers that muscles have more purpose in the body. Xoey dan Yuri bertanya pada Biseps dan Triseps kenapa Zain tidak sekuat Dada? Ayuh, ikut mereka mengakaji saiz dan fungsi otot-otot dalam tubuh Zain!

Zain is sunburnt! Xoey & Yuri tries to help and travel deep into the layers of the epidermis to meet melanocyte and find out what exactly happens after a sunburn and what affects it! Uh, oh! Kulit Zain terselar sebab terlalu lama berjemur di bawah sinaran matahari. Xoey dan Yuri segera berjumpa dengan Melanosit untuk mengkaji misteri di sebalik lapisan kulit.

Mama chides Zain for eating breakfast before brushing is teeth! Curious, Xoey & Yuri heads over to molar and find out what happens if we don't brush our teeth. Mama kata Zain tak boleh makan sarapan kalau dia tak berus gigi dahulu. Ini tak adil! Xoey dan Yuri segera berjumpa dengan Gigi Geraham untuk mendapatkan penjelasan.

Zain pees the bed! Xoey & Yuri are curious as to what had happened seeing he is too old for such incidents! They head over to the bladder, where a surprise awaits them. Xoey dan Yuri rasa seperti ada yang tak kena dengan Pundi Kencing. Mereka tak sabar untuk mengkaji misteri kenapa Zain terbuang air kecil ketika dia sedang tidur.

Xoey & Yuri pay a visit to the pancreas where they find out more about hormone and enzymes and why a well balanced blood sugar level is so important. P-A-N-K-R-E-A-S! Hormon dan Enzim bertungkus lumus menjaga fungsi Pankreas tapi, Xoey dan Yuri tak pasti untuk apa?

During vocal lessons, Zain realises he can actually reach a high pitch! Xoey & Yuri finds out how your voice can change and how the larynx actually works!

Zain's body clock has gone completely haywire! Xoey & Yuri are curious as to what a body clock actually is and finds out the importance of sleep from the mighty brain.