3CM，一個微不足道的距離，卻是結節性硬化症病人生死存亡的指標。繼走入低收入家庭的《子非魚》到凝視生死的《伴生》後，黃肇邦進一步拓展題材範圍，窺探香港藥物政策的灰色地帶。

電影追隨兩個截然不同的患病家庭，由病人生存權利開始，探索到社會公共利益，記錄著一群彷彿被社會遺棄的罕見病人，如何在社會眾多各種的訴求之中，爭取關注，爭取多活一天的或許權利。但原來人的價值始終有高低之分，在政策制定的過程中，無奈地只能淪為一堆數字，哪個值得救，四個字「成本效益」，早在他們出生的那天已有定案。

Tuberous Sclerosis Complex (TSC) is a genetic disorder that causes noncancerous tumors to grow in different parts of the body. However, the Hong Kong government has been slow to allow treatment for the disease, especially in relaxing regulations for drugs that treat the tumors.

After taking an in-depth look at ordinary citizens facing death in his critically-acclaimed documentary Snuggle, director Wong Siu-pong now turns his camera on Hong Kong’s medical system with this heartrending documentary about a young TSC patient who also lost her mother to the disease.