The Mizielińskis have their own characteristic style: colourful, intentionally naïve, childish drawings that show tens of figures and objects engaged in various narrations. As the artists put it, they create things they would want to use themselves. They use hundreds of colours, when they need a font they simply design it themselves, when they want to play a game they invent it. Their products can interest anyone, they make both youngsters and grownups happy. The creations by Hipopotam Studio are fascinating, developmental and they make people smile.
Together with the publishing house Dwie Siostry they created the book D. O. M. E. K. (H.O.U.S.E.), which shows children various houses by known architects. The book was declared Book of the Year 2008 of the Polish Section of IBBY and was later published in English, German, French, Italian, Spanish, Russian and in many other languages including Arabic and Chinese. The Mizielińskis were also responsible for the graphic design of other books from the S.E.R.I.A. (S.E.R.I.E.S.) series. The duo worked on D.E.S.I.G.N. which featured texts by Ewa Solarz (2010), and S.Z.T.U.K.A. (A.R.T.) by Sebastian Cichocki.
These projects brought the Mizielińskis great popularity. The two artists were both born in 1982 and they obtained their diplomas in 2007 from the Book Design Workshop of professor Maciej Buszewicz and Grażka Lange. As juniors in college, they founded the design studio Hipopotam Studio of which they’re still artistic directors. The duo collaborates with publishing houses such as Znak, Dwie Siostry and 40 000 Malarzy. They create book covers and graphic designs for books as well as prepare their own publications. As they say, they don’t really know how to make books for children, they actually design these publications as they would for themselves. This however is a very good method as their works are gaining popularity worldwide.
In 2011, they put out the book Miasteczko Mamoko (Welcome to Mamoko), which includes only illustrations. These drawings help those who look at them (not only children) exercise their sense of observation. The book had 2 sequels entitled Dawno Temu w Mamoko – Jesteśmy w Średniowieczu (Mamoko in the Time of Dragons) and Mamoko 3000 (The World of Mamoko in the Year 3000) which was set in the future.