Could you suggest some houseplants that are small enough to set and grow on a windowsill?

There are many, many plants small enough to grow on a windowsill. Here are a few suggestions. Cacti and succulents not only grow very slowly, but are very compact and easy to grow. They are also one of the most interesting-looking group of plants. In the flowering plant category, you could try the ever popular African violet or maybe something a little different such as a kalanchoe or miniature cyclamen. If you like trailing plants, try English ivy. Ivy grows quickly, but is easy to prune and keep at a manageable size.