From the late 1960s until his death in 1975, Yolanda Sonnabend collaborated with the biologist and embryologist C.H. Waddington. She was employed as his research assistant on various projects, and produced the artwork for his book 'Tools for Thought: how to understand and apply the latest scientific techniques of problem solving', which was intended to be a popular guide to new ways of perceiving and understanding the world’s scientific, political and ecological problems. Sonnabend’s stark and imaginative pen and ink drawings formed the perfect complement to Waddington's ideas, incorporating triangles, graphs, arrows and bird heads, although unfortunately many of her original designs did not make it into the final book, which was finally published two years after Waddington's death.