c# - Multithreading multiple forms

Question

I have one main form that starts on program in program.cs as Application.Run(new Form1());. It opens object of 2 different forms as:

Form2 obj1 = new Form2();
obj2.Show();

Form3 obj2 = new Form3();
obj3.Show();

Each form has Thread.Sleep(10000) code but the problem is that on one's Thread.Sleep execution, whole programs sleeps. I thought if one form's Thread.Sleep runs, it will not stop other form and will not affect those.